For several months, the Vista PC in my home office refused to upgrade Firefox. The first few times this happened, I uninstalled the old version of Firefox and reinstalled the new version. (Instructions for installing Firefox are provided on the Firefox support site.)
Though this allowed me to upgrade the browser, the uninstall/reinstall process took far too long. The Firefox error message instructed me to "make sure there are no other copies of Firefox running on your computer, and then restart Firefox to try again." I closed Firefox, opened the Windows Task Manager Processes list (press Ctrl+Alt+Delete, choose Start Task Manager, and click the Processes tab).
Sure enough, there was an entry for "firefox.exe *32," even though there were no Firefox windows open on the system. I selected the rogue entry and chose End Process to close it. With the phantom process gone, Firefox updated without a hitch.
Here are solutions to four other common Firefox glitches.
Conflicts with security software, outdated add-ons cause slow starts/no starts
Firefox was starting so slowly on my test PC that I began to wonder whether I actually clicked the fox icon in my Quick Launch toolbar. I soon realized I neglected to uninstall about a half-dozen Firefox add-ons I had tested several months ago and no longer used.
Once I uninstalled them in Firefox's add-ons dialog (click Tools > Add-ons > Extensions to see the list), the browser opened in a jiffy once again. Unfortunately, some slow Firefox starts aren't so easy to troubleshoot. In some instances, Firefox opens but won't load any Web pages. The Firefox Support site provides several possible causes and cures.
Likewise, if Firefox crashes when you attempt to start the program, the support site recommends that you upgrade to the latest version, try opening the browser via the Safe Mode option in the Mozilla Firefox folder on Windows' Start menu, look for conflicts with plug-ins or other software, or scan the system for malware.
Three other pages on the Firefox Support site describe fixes for crashes loading only specific pages, crashes that occur when attempting to download a file, and crashes when exiting the program.
Delete add-ons that won't go quietly
Sometimes, the option to uninstall a Firefox add-on is grayed out, even when the program isn't compatible with the latest version of the browser. That's the case for Google Gears on my test machine.
To remove such "uninstallable" extensions, open Firefox in Safe Mode, reopen the Extensions list in the browser's add-ons dialog, and see if the uninstall option is now clickable. If the Uninstall button is still grayed out, the solution entails opening your Firefox profile folder (instructions for doing so), and following the steps presented in that article for your version of the browser.
Prevent update notices when you already have the latest Firefox version
Few things about PCs are more frustrating than being told repeatedly that you successfully installed an update that's been on your system for weeks. The two reasons for this described on the Firefox support site are that you inadvertently saved the "new update was installed" tab, or Firefox is unable to save your settings file.
In the first instance, the cure involves opening the Options dialog (in Firefox 3.6, click Tools > Options > General) and making sure the Mozilla.com What's New page isn't listed as your Home Page. Possible causes for Firefox being unable to save your settings file are presented in the Firefox Support article "Preferences are not saved."
Similarly, Firefox may continue to prompt you about an available update that you've already installed. Two potential solutions are to reinstall Firefox and to open your Firefox user folder and delete two files: active-update.xml and updates.xml.
Unfortunately, Firefox sometimes forgets your autocomplete entries. First, make sure the browser is set to remember the data: in Firefox 3.6, click Tools > Options > Privacy and make sure "Remember search and form history" is checked.
If you've checked "Clear history when Firefox closes" in the same window, click the Settings button to the right and make sure Form & Search History is unchecked.