EVERY FEW DAYS I GOT "UPDATE AVAILABLE" MESSAGE, clicked the load, and the blue candy stripe showed, but never stopped and window remained open, re update v15.
5/15/12 installed update 12.0 nothing has been installed since then due to the same problem each time I get a message.
Oops I meant to link you to the Mac article, How to download and install Firefox on Mac, not the Windows version.
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
- Firefox 15.0.x: http://www.mozilla.org/en-US/firefox/all.html
- Trash the current Firefox application (e.g. open the Applications folder in the Finder and drag the Firefox application to the Trash) to do a clean (re-)install
- Install the new version that you have downloaded
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.