did you install a lot of extensions? Most members that I help with FF have similar problems, with all versions, when too many extensions are installed. If yes, remove some as well revert back to the original theme and see if it crashes, or freezes up, still.

I removed all Firefox files prior to installing 2.0, and I am with out issues.

I do have a gripe with the stupid new 'x' or close tab feature, and stacking of tabs.