You need to upgrade to FF4. (Presumably as SproutCore 2 gets closer to release, it will get better error handling. But the old Firefox is the reason is won't render.)
3.6 barely runs on my machine as it is; a number of clients are asking me to downgrade them from 4 to 3.6 because of stupid issues like not saving your tabs by default when you close the browser. I have about thirty tabs open in my browser right now, and the last time I upgraded Firefox, it didn't bother to save any of them the next it launched.
I just can't be arsed to go to that much trouble over one website.
edit: (removed snarky edit.)
Also you can "pin as app tabs" anything that you like to consistently have open.
FF4 also runs considerably faster. I can't imagine wanting to downgrade ...