C:\Documents and Settings\<user>\Local Settings\Application Data\Mozilla\Firefox\Mozilla Firefox\updates
(%USERPROFILE%\Local Settings\Application Data\Mozilla\Firefox\Mozilla Firefox)

Remove the files in the updates and updates\0 folder.<br /> You may need to delete active-update.xml and updates.xml as well if present. XP: C:\Documents and Settings\&lt;user&gt;\Local Settings\Application Data\Mozilla\Firefox\Mozilla Firefox\updates (%USERPROFILE%\Local Settings\Application Data\Mozilla\Firefox\Mozilla Firefox) * http://kb.mozillazine.org/Software_Update (Software Update not working properly) ---- If you have problems with updating then best is to download the full version and uninstall the currently installed version. You may need to remove the Firefox program folder to do a clean install of the new version. Do a clean (re-)install: Download a fresh Firefox copy and save the file to the desktop. * Firefox 4.0.x: http://www.mozilla.com/en-US/firefox/all.html * Firefox 3.6.x: http://www.mozilla.com/en-US/firefox/all-older.html * Uninstall your current Firefox version. * Do not remove personal data when you uninstall the current version. Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer. * It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling. * It may not be necessary to create a new profile, so first try if it works with your current profile and if not then create a new profile. You do not need to create a new profile, that is not necessary for this issue Your bookmarks and other profile data are stored elsewhere in the [http://kb.mozillazine.org/Profile_folder_-_Firefox Firefox Profile Folder] and won't be affected by a reinstall, but make sure that you do not select to remove personal data if you uninstall Firefox.