It is possible that there is a problem with the file(s) that store the extensions registry.

Delete the extensions.* files (e.g. extensions.sqlite, extensions.ini) and compatibility.ini in the Firefox profile folder to reset the extensions registry.

• https://support.mozilla.org/kb/Profiles

New files will be created when required.

See "Corrupt extension files":

• http://kb.mozillazine.org/Unable_to_install_themes_or_extensions
• https://support.mozilla.org/kb/Unable+to+install+add-ons

If you see disabled or not compatible extensions in "Firefox/Tools > Add-ons > Extensions" then click the Tools button at the left end side of the Search Bar ("Find Updates" button in older Firefox versions) to check if there is a compatibility update available.

If this hasn't helped then also delete the addons.sqlite file.

Thanks cor-el. That partially solved things. The Roboform toolbar has now re-appeared. Oddly, I didn't reinstall it and it isn't listed in extensions. But the toolbar is there and working.

The bigger problem, though, is that my other extensions still don't work after reinstalling them. (The file deletions deleted the extensions, which I assume is what's supposed to happen. So I tried reinstalling one or two of them.)

You may need to exit Firefox, delete extensions.sqlite (and if it exists, extensions.ini), and then restart Firefox to trigger Firefox re-detecting your existing extensions. Making changes without restarting may lead to mixed results.

Thanks jscher2000, but I tried that (including restarting FF afterward).

It didn't redetect my extensions, btw -- they were deleted entirely.

I know you want to do a Reset last, so the next thought is: perhaps a program file is corrupted?

I suggest making a backup your active settings folder (your Firefox profile folder) before the next step. This article has tips: Back up and restore information in Firefox profiles.

Try a Clean reinstall. This involves removing Firefox program files (not settings) and then reinstalling Firefox. Please follow these steps:

Note: You might want to print these steps or view them in another browser.

1. Download the latest Desktop version of Firefox for your language from https://www.mozilla.org/firefox/all/ and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu).
3. Open C:\Program Files (x86)\ and drag the "Mozilla Firefox" folder to a temporary location such as Documents (you can delete it later after confirming it doesn't contain any system-level add-ons you want to rescue)
4. Now, go ahead and reinstall Firefox:
   • Double-click the downloaded installation file and go through the steps of the installation wizard.
   • Once the wizard is finished, choose to directly open Firefox after clicking the Finish button. Firefox should find your profile data automatically.

Any luck?

Did you try to do an update check on the about:addons page to make Firefox check for possible compatibility updates?

You can also try to rename or delete the prefs.js file and possible numbered prefs-##.js files and a possible user.js file to reset all prefs to the default value.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

I haven't been able to work on this today so far, but am beginning to think I should bite the bullet and Reset or uninstall and reinstall. I can save my sessionstore.js and reimport it afterward. Is there anything else that might be essential?

Also, someone else is suggesting that I might resolve the problem by setting up a new profile. Does that sound like a possibility?

Thanks!

Hi Greenbergman,

• sessionstore.js only contains windows and tabs from your most recent session. Definitely worth saving, but there is a huge amount of other valuable data in your profile.

• Reset carries over a lot of your personal data (e.g., bookmarks) but drops other data (e.g., last session). Please refer to the help article for details.

• Uninstall (without removing personal data) and reinstall can repair program files, but otherwise is unlikely to make much difference.

• A new profile will look like a fresh install of Firefox. If it works well, you know there is a problem in your regular profile. This article describes how you can use the Profile Manager to create a new profile, or switch between different profiles: Profile Manager - Create, remove or switch Firefox profiles. I recommend doing a backup of all profiles before deleting one, lest you accidentally select the wrong one from the dialog (yikes). If the new profile is good, we can have further discussions about the best strategy for migrating your settings. The most automatic is to start back up in your regular profile and use the Reset feature.

Thanks all. I ended up doing a Reset and then just had to paste my sessionstore file and reinstall extensions. Everything seems ok now.