Bug 428362 - "Unhandled exception in SanitizeListener constructor". r=gavin, a=beltzner.

browser/base/content/browser.js

@@ -1271,7 +1271,7 @@ function SanitizeListener()
     gPrefService.clearUserPref(this.didSanitizeDomain);
     // We need to persist this preference change, since we want to
     // check it at next app start even if the browser exits abruptly
-    gPrefService.savePrefFile(null);
+    gPrefService.QueryInterface(Ci.nsIPrefService).savePrefFile(null);
   }
 }