Firefox: Locating Erring ExtensionsFirefox: Locating Erring Extensions

If you suspect an extension or extensions is causing Firefox to act up, here's how to test your theory: Run Firefox in Safe Mode, which reverts the browser temporarily to the default theme and disables all extensions.

You can do that in Windows by clicking on the "Mozilla Firefox (Safe Mode)" icon in the Mozilla Firefox application group on the Start menu.

Or, if the icon is unavailable, run "firefox.exe" -safe-mode" from the command line. (Follow this link for instructions on how to run Firefox in Safe Mode on the Mac and Linux.)

If the problem goes away in Safe Mode, then an extension or extensions was the cause of the problem. Uninstall all your extensions. You may even have to uninstall Firefox, and then delete its settings and remaining files.

To uninstall Firefox, its settings and remaining files, first save a copy of your bookmarks. To locate the bookmarks, look in a directory called "C:\Documents and Settings\username\Application Data\Mozilla\Firefox\Profiles\". "Username" in the preceding example will be your user name -- for example, jsmith.

Below that directory you'll find one with a funny name, with random numbers and characters, like "k4wyz7kz.default" or something like that. Inside that directory is your bookmarks.html file. That's the one you want to save. Make a copy of it and store it elsewhere on your hard disk.

Next, remove Firefox using the Add/Remove Software utility in Windows.

Then delete the Firefox settings and files. To do that, delete the folder "C:\Documents and Settings\username\Application Data\Mozilla\Firefox."

Then re-install the browser. Start adding your extensions one at a time; when your problem recurs, you can assume that the last extension you installed was the one that caused it. Uninstall it. You may have to go back to the beginning and uninstall everything if the faulty extension has bollixed up your browser settings.

Lastly, you'll want to get your old bookmarks back. Click on Firefox's Bookmarks menu, then select "Manage Bookmarks..." When the bookmark manager comes up, click the File menu, then Import. A wizard will come up, asking you whether you want to import from Internet Explorer or a file. Click "From File," then navigate to the spot where you put your bookmarks.htm file, click on that file, then click "Open."

Mitch Wagner is editor of Security Pipeline.