This has got to be one of the most annoying errors associated with the popular web browser Mozilla FireFox. If FF encounters a problem when an update is being applied, an error message "Software Update Failed. The update could not be installed…” will be displayed every time you try to start the application. I was unfortunate enough to face the issue myself and luckily managed to solve it wihout having to waste a lots of time. If you are encountering the same issue, here are a few things you can try to hopefully get the problem sorted out.
Note: Before you try any of the fixes below please backup your personal settings, bookmarks and saved passwords.
- Browse to Start Menu –> Programs –> Mozilla FireFox and right click the FireFox shortcut. Choose ‘run as administrator’ from the menu and execute. If it doesn’t work the first time, try 2-3 times. If FF cannot update due to insufficient user account privileges this should solve it.
- Browse to C:\Users\USERNAME\AppData\Local\Mozilla\FireFox\Mozilla FireFox (path is different in Windows XP). Delete the updates directory, updates.xml and active-update.xml files if they are present. Start FireFox. If FF encountered an error during the update process, this should clear the last update and start fresh from the beginning.
- If it still doesn’t work, go to Mozilla download page and download the latest version of FireFox. Without uninstalling the existing version, execute the new setup. If the existing version is 3.X/3.5.X, newest version will be installed over the existing installation, clearing any update mishaps.