Don't use the current Bon Echo nightlies (i.e., Firefox 2.0a), from the one released Monday to now. There's a wicked nasty crash bug. For many people, it is completely unusable right now. If you are interested in nightlies, wait for
Bug 339861
crash since 20060530 hourly on the Firefox 2 branch [@ ntdll.dll] to be resolved. Or just get the 2.0a3 release, which just barely predates the checkin that caused this bug.