I did a little digging and good news, you're not the only one! OK, that probably doesn't make you feel much better. Haven't found anybody that knows why this is happening yet, just that the forum software and firefox 1.5 aren't getting along for the occasional user. Reported crashes and hangs.
Something that has worked for at least one user is disabling viewing of avatars in your user control panel. In the "Options" page there is a "Show Avatars" checkbox under the "Thread Display Options" section. If this works for you, please report back.
Threaded Mode
