diff --git a/common/modules/dom.jsm b/common/modules/dom.jsm
index 98b3cbc4..1167feba 100644
--- a/common/modules/dom.jsm
+++ b/common/modules/dom.jsm
@@ -1540,6 +1540,12 @@ var DOM = Class("DOM", {
         function tag(args, namespaces) {
             let _namespaces = namespaces;
 
+            // Deal with common error case
+            if (args == null) {
+                util.reportError(Error("Unexpected null when processing XML."));
+                args = ["html:i", {}, "[NULL]"];
+            }
+
             if (isinstance(args, ["String", "Number", "Boolean", _]))
                 return doc.createTextNode(args);
             if (isXML(args))
@@ -1575,7 +1581,7 @@ var DOM = Class("DOM", {
             for (var key in attr) {
                 if (/^xmlns(?:$|:)/.test(key)) {
                     if (_namespaces === namespaces)
-                        namespaces = update({}, namespaces);
+                        namespaces = Object.create(namespaces);
 
                     namespaces[key.substr(6)] = namespaces[attr[key]] || attr[key];
                 }}
diff --git a/common/modules/prefs.jsm b/common/modules/prefs.jsm
index f801f947..b0fdd176 100644
--- a/common/modules/prefs.jsm
+++ b/common/modules/prefs.jsm
@@ -111,10 +111,11 @@ var Prefs = Module("prefs", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference])
             switch (type) {
             case Ci.nsIPrefBranch.PREF_STRING:
                 let value = this.branch.getComplexValue(name, Ci.nsISupportsString).data;
-                // try in case it's a localized string (will throw an exception if not)
-                if (!this.branch.prefIsLocked(name) && !this.branch.prefHasUserValue(name) &&
-                    RegExp("chrome://.+/locale/.+\\.properties").test(value))
-                        value = this.branch.getComplexValue(name, Ci.nsIPrefLocalizedString).data;
+                try {
+                    if (/^[a-z0-9-]+:/i.test(value))
+                    value = this.branch.getComplexValue(name, Ci.nsIPrefLocalizedString).data;
+                }
+                catch (e) {}
                 return value;
             case Ci.nsIPrefBranch.PREF_INT:
                 return this.branch.getIntPref(name);