probably corrupted session data in your ffox profile. uninstall ffox. Then open a terminal:
[user@localhost:~]$ cd ~/.mozilla
[user@localhost:~/.mozilla]$ mv firefox firefox-prev
this will remove (but save) your old profile settings (bookmarks, session, plugins, etc)
reinstall ffox, it should ask you the bookmark importing or whatever and show you the welcome to ffox first time page. After that, you can copy your plugins, bookmarks, add-ons (xpi?) from ~/.mozilla/firefox-prev/. But be careful not to create another corrupted profile and waste your time.