I've had FF 2 for quite a while and it has been rock solid. I wonder why they decided to go with 3.0 so soon after the last release as well. Although it is in Alpha it might take a long lead time before its release.
Google Preview HTF Toolbar Colorful Tabs Download Manager Tweak Download Status Bar Firefox Extension Backup Google Toolbar For Firefox IE Tab Link Preview Nuke Anything Enhanced Pop Up Sound Update Notifier
I am guessing any one or combination of those could be the reason for Firefox 2 crashing.