diff --git a/common/content/abbreviations.js b/common/content/abbreviations.js
index 09097e0a..1b3f76a3 100644
--- a/common/content/abbreviations.js
+++ b/common/content/abbreviations.js
@@ -8,7 +8,7 @@
 
 /** @scope modules */
 
-const Abbreviation = Class("Abbreviation", {
+var Abbreviation = Class("Abbreviation", {
     init: function (modes, lhs, rhs) {
         this.modes = modes.sort();
         this.lhs = lhs;
@@ -41,7 +41,7 @@ const Abbreviation = Class("Abbreviation", {
     }
 });
 
-const Abbreviations = Module("abbreviations", {
+var Abbreviations = Module("abbreviations", {
     init: function () {
         this.abbrevs = {};
 
diff --git a/common/content/autocommands.js b/common/content/autocommands.js
index 66a66f73..802b1ecd 100644
--- a/common/content/autocommands.js
+++ b/common/content/autocommands.js
@@ -8,12 +8,12 @@
 
 /** @scope modules */
 
-const AutoCommand = Struct("event", "pattern", "command");
+var AutoCommand = Struct("event", "pattern", "command");
 
 /**
  * @instance autocommands
  */
-const AutoCommands = Module("autocommands", {
+var AutoCommands = Module("autocommands", {
     init: function () {
         this._store = [];
     },
diff --git a/common/content/bookmarks.js b/common/content/bookmarks.js
index 440a65eb..b6643e87 100644
--- a/common/content/bookmarks.js
+++ b/common/content/bookmarks.js
@@ -6,10 +6,10 @@
 // given in the LICENSE.txt file included with this file.
 "use strict";
 
-const DEFAULT_FAVICON = "chrome://mozapps/skin/places/defaultFavicon.png";
+var DEFAULT_FAVICON = "chrome://mozapps/skin/places/defaultFavicon.png";
 
 // also includes methods for dealing with keywords and search engines
-const Bookmarks = Module("bookmarks", {
+var Bookmarks = Module("bookmarks", {
     init: function () {
         storage.addObserver("bookmark-cache", function (key, event, arg) {
             if (["add", "change", "remove"].indexOf(event) >= 0)
diff --git a/common/content/browser.js b/common/content/browser.js
index 7bc25097..6ceef9bf 100644
--- a/common/content/browser.js
+++ b/common/content/browser.js
@@ -11,7 +11,7 @@
 /**
  * @instance browser
  */
-const Browser = Module("browser", {
+var Browser = Module("browser", {
 }, {
     climbUrlPath: function (count) {
         let url = util.newURI(buffer.URL);
diff --git a/common/content/buffer.js b/common/content/buffer.js
index 04dc93ed..5c2f0c97 100644
--- a/common/content/buffer.js
+++ b/common/content/buffer.js
@@ -8,7 +8,7 @@
 
 /** @scope modules */
 
-const Point = Struct("x", "y");
+var Point = Struct("x", "y");
 
 /**
  * A class to manage the primary web content buffer. The name comes
@@ -16,7 +16,7 @@ const Point = Struct("x", "y");
  * files.
  * @instance buffer
  */
-const Buffer = Module("buffer", {
+var Buffer = Module("buffer", {
     init: function () {
         this.evaluateXPath = util.evaluateXPath;
         this.pageInfo = {};
diff --git a/common/content/commandline.js b/common/content/commandline.js
index 1c0647bb..18865e97 100644
--- a/common/content/commandline.js
+++ b/common/content/commandline.js
@@ -8,7 +8,7 @@
 
 /** @scope modules */
 
-const CommandWidgets = Class("CommandWidgets", {
+var CommandWidgets = Class("CommandWidgets", {
     init: function () {
         this.elements = {};
         this.addElement({
@@ -200,7 +200,7 @@ const CommandWidgets = Class("CommandWidgets", {
  * It consists of a prompt and command field be sure to only create objects of
  * this class when the chrome is ready.
  */
-const CommandLine = Module("commandline", {
+var CommandLine = Module("commandline", {
     init: function () {
         const self = this;
 
@@ -1766,7 +1766,7 @@ const CommandLine = Module("commandline", {
  *     must be in its own container element, whose height it will update as
  *     necessary.
  */
-const ItemList = Class("ItemList", {
+var ItemList = Class("ItemList", {
     init: function (id) {
         this._completionElements = [];
 
diff --git a/common/content/commands.js b/common/content/commands.js
index c508757d..b650f464 100644
--- a/common/content/commands.js
+++ b/common/content/commands.js
@@ -35,12 +35,12 @@
  * @property {string} description A description of the option
  */
 
-const CommandOption = Struct("names", "type", "validator", "completer", "multiple", "description", "default");
+var CommandOption = Struct("names", "type", "validator", "completer", "multiple", "description", "default");
 CommandOption.defaultValue("description", function () "");
 CommandOption.defaultValue("type", function () CommandOption.NOARG);
 CommandOption.defaultValue("multiple", function () false);
 
-const ArgType = Struct("description", "parse");
+var ArgType = Struct("description", "parse");
 update(CommandOption, {
     /**
      * @property {object} The option argument is unspecified. Any argument
@@ -108,7 +108,7 @@ update(CommandOption, {
  * @optional
  * @private
  */
-const Command = Class("Command", {
+var Command = Class("Command", {
     init: function (specs, description, action, extraInfo) {
         specs = Array.concat(specs); // XXX
         let parsedSpecs = Command.parseSpecs(specs);
@@ -377,7 +377,7 @@ const Command = Class("Command", {
 });
 
 // Prototype.
-const ex = {
+var ex = {
     _args: function (cmd, args) {
         args = Array.slice(args);
 
@@ -427,7 +427,7 @@ const ex = {
 /**
  * @instance commands
  */
-const Commands = Module("commands", {
+var Commands = Module("commands", {
     init: function () {
         this._exCommands = [];
         this._exMap = {};
diff --git a/common/content/completion.js b/common/content/completion.js
index c58c604f..cc9d6bf1 100644
--- a/common/content/completion.js
+++ b/common/content/completion.js
@@ -26,7 +26,7 @@
  * @author Kris Maglione <maglione.k@gmail.com>
  * @constructor
  */
-const CompletionContext = Class("CompletionContext", {
+var CompletionContext = Class("CompletionContext", {
     init: function (editor, name, offset) {
         if (!name)
             name = "";
@@ -825,7 +825,7 @@ const CompletionContext = Class("CompletionContext", {
 /**
  * @instance completion
  */
-const Completion = Module("completion", {
+var Completion = Module("completion", {
     init: function () {
     },
 
diff --git a/common/content/configbase.js b/common/content/configbase.js
index e9e9800d..b068dac7 100644
--- a/common/content/configbase.js
+++ b/common/content/configbase.js
@@ -6,7 +6,7 @@
 // given in the LICENSE.txt file included with this file.
 "use strict";
 
-const ConfigBase = Class(ModuleBase, {
+var ConfigBase = Class(ModuleBase, {
     /**
      * Called on dactyl startup to allow for any arbitrary application-specific
      * initialization code. Must call superclass's init function.
diff --git a/common/content/dactyl.js b/common/content/dactyl.js
index dda0c8d8..ca2e011a 100644
--- a/common/content/dactyl.js
+++ b/common/content/dactyl.js
@@ -12,14 +12,14 @@ default xml namespace = XHTML;
 XML.ignoreWhitespace = false;
 XML.prettyPrinting = false;
 
-const plugins = { __proto__: modules };
-const userContext = newContext(modules);
+var plugins = { __proto__: modules };
+var userContext = newContext(modules);
 
-const EVAL_ERROR = "__dactyl_eval_error";
-const EVAL_RESULT = "__dactyl_eval_result";
-const EVAL_STRING = "__dactyl_eval_string";
+var EVAL_ERROR = "__dactyl_eval_error";
+var EVAL_RESULT = "__dactyl_eval_result";
+var EVAL_STRING = "__dactyl_eval_string";
 
-const Dactyl = Module("dactyl", {
+var Dactyl = Module("dactyl", XPCOM(Ci.nsISupportsWeakReference, ModuleBase), {
     init: function () {
         window.dactyl = this;
         // cheap attempt at compatibility
diff --git a/common/content/editor.js b/common/content/editor.js
index 5945f4fb..b6730218 100644
--- a/common/content/editor.js
+++ b/common/content/editor.js
@@ -10,7 +10,7 @@
 // http://developer.mozilla.org/en/docs/Editor_Embedding_Guide
 
 /** @instance editor */
-const Editor = Module("editor", {
+var Editor = Module("editor", {
     get isCaret() modes.getStack(1).main == modes.CARET,
     get isTextEdit() modes.getStack(1).main == modes.TEXT_EDIT,
 
diff --git a/common/content/events.js b/common/content/events.js
index 6b6b5c75..b9c4f5c7 100644
--- a/common/content/events.js
+++ b/common/content/events.js
@@ -11,7 +11,7 @@
 /**
  * @instance events
  */
-const Events = Module("events", {
+var Events = Module("events", {
     init: function () {
         this._fullscreen = window.fullScreen;
         this._lastFocus = null;
diff --git a/common/content/finder.js b/common/content/finder.js
index 91a671da..26c093e2 100644
--- a/common/content/finder.js
+++ b/common/content/finder.js
@@ -7,7 +7,7 @@
 /** @scope modules */
 
 /** @instance rangefinder */
-const RangeFinder = Module("rangefinder", {
+var RangeFinder = Module("rangefinder", {
     init: function () {
         this.lastFindPattern = "";
     },
@@ -251,7 +251,7 @@ const RangeFinder = Module("rangefinder", {
  * documents, and represents a major detriment to productivity where
  * large amounts of data are concerned (e.g., for API documents).
  */
-const RangeFind = Class("RangeFind", {
+var RangeFind = Class("RangeFind", {
     init: function (matchCase, backward, elementPath, regexp) {
         this.window = Cu.getWeakReference(window);
         this.baseDocument = Cu.getWeakReference(content.document);
diff --git a/common/content/hints.js b/common/content/hints.js
index 61140e30..2785b09d 100644
--- a/common/content/hints.js
+++ b/common/content/hints.js
@@ -9,7 +9,7 @@
 /** @scope modules */
 /** @instance hints */
 
-const Hints = Module("hints", {
+var Hints = Module("hints", {
     init: function init() {
         const self = this;
 
diff --git a/common/content/history.js b/common/content/history.js
index 1d8e791c..1e648fd6 100644
--- a/common/content/history.js
+++ b/common/content/history.js
@@ -6,7 +6,7 @@
 // given in the LICENSE.txt file included with this file.
 "use strict";
 
-const History = Module("history", {
+var History = Module("history", {
     get format() bookmarks.format,
 
     get service() services.history,
diff --git a/common/content/io.js b/common/content/io.js
index 29731ead..0f923b28 100644
--- a/common/content/io.js
+++ b/common/content/io.js
@@ -38,7 +38,7 @@ function Script(file) {
  * Provides a basic interface to common system I/O operations.
  * @instance io
  */
-const IO = Module("io", {
+var IO = Module("io", {
     init: function () {
         this._processDir = services.directory.get("CurWorkD", Ci.nsIFile);
         this._cwd = this._processDir.path;
diff --git a/common/content/javascript.js b/common/content/javascript.js
index b29989bd..9325aa91 100644
--- a/common/content/javascript.js
+++ b/common/content/javascript.js
@@ -6,7 +6,7 @@
 
 // TODO: Clean this up.
 
-const JavaScript = Module("javascript", {
+var JavaScript = Module("javascript", {
     init: function () {
         this._stack = [];
         this._functions = [];
diff --git a/common/content/mappings.js b/common/content/mappings.js
index d9281d88..d3a2a25d 100644
--- a/common/content/mappings.js
+++ b/common/content/mappings.js
@@ -29,7 +29,7 @@
  * @optional
  * @private
  */
-const Map = Class("Map", {
+var Map = Class("Map", {
     init: function (modes, keys, description, action, extraInfo) {
         modes = Array.concat(modes).map(function (m) isObject(m) ? m.mask : m);
         if (!modes.every(util.identity))
@@ -127,7 +127,7 @@ const Map = Class("Map", {
 /**
  * @instance mappings
  */
-const Mappings = Module("mappings", {
+var Mappings = Module("mappings", {
     init: function () {
         this._main = []; // default mappings
         this._user = []; // user created mappings
diff --git a/common/content/marks.js b/common/content/marks.js
index c1a515b7..93e5221c 100644
--- a/common/content/marks.js
+++ b/common/content/marks.js
@@ -10,7 +10,7 @@
  * @scope modules
  * @instance marks
  */
-const Marks = Module("marks", {
+var Marks = Module("marks", {
     init: function init() {
         function replacer(key, val) val instanceof Ci.nsISupports ? null : val;
         this._localMarks = storage.newMap("local-marks", { privateData: true, replacer: replacer, store: true });
diff --git a/common/content/modes.js b/common/content/modes.js
index bde52ba6..aab3b314 100644
--- a/common/content/modes.js
+++ b/common/content/modes.js
@@ -8,7 +8,7 @@
 
 /** @scope modules */
 
-const Modes = Module("modes", {
+var Modes = Module("modes", {
     init: function () {
         this.modeChars = {};
         this._main = 1;     // NORMAL
diff --git a/common/content/modules.js b/common/content/modules.js
index a1ed1640..df15743b 100644
--- a/common/content/modules.js
+++ b/common/content/modules.js
@@ -8,7 +8,7 @@
  * @class ModuleBase
  * The base class for all modules.
  */
-const ModuleBase = Class("ModuleBase", {
+var ModuleBase = Class("ModuleBase", {
     /**
      * @property {[string]} A list of module prerequisites which
      * must be initialized before this module is loaded.
diff --git a/common/content/options.js b/common/content/options.js
index 1f06f7e0..3df9e724 100644
--- a/common/content/options.js
+++ b/common/content/options.js
@@ -34,7 +34,7 @@ let ValueError = Class("ValueError", ErrorBase);
  * @optional
  * @private
  */
-const Option = Class("Option", {
+var Option = Class("Option", {
     init: function (names, description, type, defaultValue, extraInfo) {
         this.name = names[0];
         this.names = names;
@@ -618,7 +618,7 @@ const Option = Class("Option", {
 /**
  * @instance options
  */
-const Options = Module("options", {
+var Options = Module("options", {
     init: function () {
         this.needInit = [];
         this._options = [];
diff --git a/common/content/quickmarks.js b/common/content/quickmarks.js
index d41a6719..47ca77f0 100644
--- a/common/content/quickmarks.js
+++ b/common/content/quickmarks.js
@@ -11,7 +11,7 @@
 /**
 * @instance quickmarks
 */
-const QuickMarks = Module("quickmarks", {
+var QuickMarks = Module("quickmarks", {
     init: function () {
         this._qmarks = storage.newMap("quickmarks", { store: true });
         storage.addObserver("quickmarks", function () {
diff --git a/common/content/statusline.js b/common/content/statusline.js
index 7914744c..07695b44 100644
--- a/common/content/statusline.js
+++ b/common/content/statusline.js
@@ -8,7 +8,7 @@
 
 /** @scope modules */
 
-const StatusLine = Module("statusline", {
+var StatusLine = Module("statusline", {
     init: function () {
         this._statusLine = document.getElementById("status-bar");
         this.statusBar = document.getElementById("addon-bar") || this._statusLine;
diff --git a/common/content/tabs.js b/common/content/tabs.js
index 5337abc9..f7a6ad5f 100644
--- a/common/content/tabs.js
+++ b/common/content/tabs.js
@@ -13,7 +13,7 @@
 /**
  * @instance tabs
  */
-const Tabs = Module("tabs", {
+var Tabs = Module("tabs", {
     init: function () {
         this._alternates = [config.tabbrowser.mCurrentTab, null];
 
diff --git a/common/modules/base.jsm b/common/modules/base.jsm
index 7de7cb39..765247f4 100644
--- a/common/modules/base.jsm
+++ b/common/modules/base.jsm
@@ -13,19 +13,19 @@ if (!JSMLoader)
             dump("dactyl: load: " + url + "\n");
             if (this.stale[url]) {
                 delete this.stale[url];
-                dump("dactyl: load stale\n");
-
                 let global = this.globals[url];
+
                 for each (let prop in Object.getOwnPropertyNames(global))
                     try {
-                        if (!set.has(this.builtin, prop) && [this, set].indexOf(global[prop]) < 0)
+                        if (!set.has(this.builtin, prop) &&
+                            [this, set].indexOf(Object.getOwnPropertyDescriptor(global, prop).value) < 0)
                             delete global[prop];
                     }
                     catch (e) {}
 
                 Components.classes["@mozilla.org/moz/jssubscript-loader;1"]
                           .getService(Components.interfaces.mozIJSSubScriptLoader)
-                          .loadSubScript(url, this.globals[url]);
+                          .loadSubScript(url, global);
                 dump("dactyl: load reloaded: " + url + "\n");
             }
             Components.utils.import(url, target);
@@ -859,10 +859,10 @@ Class.prototype = {
      */
     timeout: function (callback, timeout) {
         const self = this;
-        let notify = { notify: function notify(timer) { try { callback.apply(self); } catch (e) { util.reportError(e); } } };
-        let timer = services.Timer();
-        timer.initWithCallback(notify, timeout || 0, timer.TYPE_ONE_SHOT);
-        return timer;
+        function notify(timer) {
+            util.trapErrors(callback, self);
+        }
+        return services.Timer(notify, timeout || 0, services.Timer.TYPE_ONE_SHOT);;
     }
 };
 memoize(Class.prototype, "closure", function () {
diff --git a/common/modules/util.jsm b/common/modules/util.jsm
index ac8410e5..0fcdc920 100644
--- a/common/modules/util.jsm
+++ b/common/modules/util.jsm
@@ -23,7 +23,7 @@ default xml namespace = XHTML;
 
 memoize(this, "Commands", function () {
     // FIXME
-    let obj = {};
+    let obj = { Module: Class };
     services.subscriptLoader.loadSubScript("chrome://dactyl/content/commands.js", obj);
     return obj.Commands;
 });
@@ -94,20 +94,28 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
     addObserver: function (obj) {
         let observers = obj._observe || obj.observe;
         obj._observe = observers;
+
         function register(meth) {
-            services.observer[meth](obj, "quit-application", true);
-            services.observer[meth](obj, "dactyl-cleanup", true);
-            for (let target in keys(observers))
-                services.observer[meth](obj, target, true);
+            for (let target in set(["dactyl-cleanup", "quit-application"].concat(Object.keys(observers))))
+                try {
+                    services.observer[meth](obj, target, true);
+                }
+                catch (e) {}
         }
         Class.replaceProperty(obj, "observe",
             function (subject, target, data) {
-                if (target == "quit-application" || target == "dactyl-cleanup")
-                    register("removeObserver");
-                if (observers[target])
-                    observers[target].call(obj, subject, data);
+                try {
+                    if (target == "quit-application" || target == "dactyl-cleanup")
+                        register("removeObserver");
+                    if (observers[target])
+                        observers[target].call(obj, subject, data);
+                }
+                catch (e) {
+                    util.reportError(e);
+                }
             });
-        obj.observe.unRegister = function () register("removeObserver");
+
+        obj.observe.unregister = function () register("removeObserver");
         register("addObserver");
     },
 
@@ -457,6 +465,14 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
      */
     dump: defineModule.dump,
 
+    stackLines: function (stack) {
+        let lines = [];
+        let match, re = /([^]*?)(@.*?)(?:\n|$)/g;
+        while (match = re.exec(stack))
+            lines.push(match[1].replace(/\n/g, "\\n").substr(0, 80) + match[2]);
+        return lines;
+    },
+
     /**
      * Dumps a stack trace to the console.
      *
@@ -464,9 +480,8 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
      * @param {number} frames The number of frames to print.
      */
     dumpStack: function dumpStack(msg, frames) {
-        let stack = Error().stack.replace(/(?:.*\n){2}/, "");
-        if (frames != null)
-            [stack] = stack.match(RegExp("(?:.*\n){0," + frames + "}"));
+        let stack = util.stackLines(Error().stack);
+        stack = stack.slice(2, 2 + (frames || 0)).join("\n");
         util.dump((arguments.length == 0 ? "Stack" : msg) + "\n" + stack + "\n");
     },
 
@@ -1126,7 +1141,7 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
         try {
             let obj = update({}, error, {
                 toString: function () String(error),
-                stack: <>{String.replace(error.stack || Error().stack, /^/mg, "\t")}</>
+                stack: <>{util.stackLines(String(error.stack || Error().stack)).join("\n").replace(/^/mg, "\t")}</>
             });
 
             this.errors.push([new Date, obj + "\n" + obj.stack]);
@@ -1140,7 +1155,7 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
         catch (e) {
             try {
                 this.dump(String(error));
-                this.dump(error.stack)
+                this.dump(util.stackLines(error.stack).join("\n"))
             }
             catch (e) { dump(e + "\n"); }
         }