this is for mac
Your user agent identifies you a Firefox 3.0.8
To be sure you can check this:
If there are problems with updating or with the permissions then easiest is to download the full version and trash the currently installed version to do a clean install of the new version.
Download a new copy of the Firefox program and save the disk image (dmg) file to the desktop
Your profile data is stored elsewhere in the Firefox Profile Folder, so you won't lose your bookmarks and other personal data if you uninstall and (re)install Firefox.