FF2.0 has crashed more for me then 1.5, however I did not do a clean install, and I re-installed with a different language then what I had. (1.5EN-US, 2.0EN-US, 2.0EN-UK). I'm going to uninstall then reinstall, see if it fixes it. On my other PC, I have not had any crashing problems like on this one.
Are the crashes reproduceable? Do they only occur under certain circumstances? If so, it would probably be helpful to file a bug report. If not, then it'll be pretty hard to help. Also, what type of "crashing" are you talking about? Are you getting any error messages?
FF stops responding [program hard-locking, windows works fine, CPU% goes up to 90% or so and stays there for 5 mins at a time) for no reason that I can find. The sites may have flash but thats it. It is entirely not reproducable (I have been unable to do so), after I ctrl+alt+del it, restart it again, hit "restore session" everything works perfectly again for the next few days. No embeded content, no Java, no PDFs, no quicktime, no realplayer. It is certainly not every hour, just common enough for me to notice it more then previous versions.