Is Firefox behaving problematic? Just like Windows, Firefox has a “Safe Mode” so you can start it up and fix things. Select “Firefox (Safe Mode)” in the Start menu. This will disable many things to get it started. It also allows you to clear out certain things to fix the problem. Be careful with this, but if you’re having a problem this can be a big help.
Still have problems? Check the Mozillazine forums where there are many helpful users willing to help out if you ask nicely.