Created attachment 382601 [details] [diff] [review] patch (check pref type first) Suppose the browser.tabs.autoHide preference doesn't exist (because a corporate consumer is updating their Firefox base). In BrowserStartup(), prepareForStartup() didn't catch the exception. delayedStartup() never executes, and gSessionHistoryObserver is never added. The result is this assertion on shutdown: ###!!! ASSERTION: Oops! You're asking for a weak reference to an object that doesn't support that.: 'factoryPtr', file c:/svn/ff_1.0_FF3.5/fx-debug/xpcom/build/nsWeakReference.cpp, line 109
Comment on attachment 382601 [details] [diff] [review] patch (check pref type first) This pref is in firefox.js, so if you're hitting this you've done something pretty horrible to your Firefox that you should avoid doing!