Not sure if it is the cause of the problem here, and I haven't installed 0.9 myself yet, but I just happened to be reading a review of FireFox 0.9 today - http://www.madpenguin.org/cms/html/47/1695.html - that mentioned a similar problem on Fedora Core 2. I think the problem was related to the default install having read-only permissions in non-root directories. Without knowing anything more and not having tried it yet, that's my best guess.