I had the same thing happen to me. When my firefox updated itself to the new version I was unable to clear my history and cookies. So I just went with it. Then I had to update flash player and the same shit happened to me. Every time I viewed something with flash, mozilla crashed. I wound up saving all my bookmarks, uninstalling firefox and flash. Reinstalled both and havent had any problems since. I think the problem to be honest was with firefox update.