The new Firefox (0.9.3) creates its user configuration files in ~/.mozilla/firefox. I had the same problem on a SuSE distro (I had run the installation with sudo by habit) and it set the user and group ownerships to root.

Look in your home directory for a hidden folder named .mozilla with #>ls -al

If it's there, then switch to root and type the following:

#>chown -R username .mozilla

#>chgrp -R users .mozilla

...now when I start Firefox, I get:
(QFA)Talkback error: Can't initialize.

but firefox starts right up without a problem.

hth,
grav