One reason for this problem to occur would be some corruption in Firefox's database of extensions. You can force Firefox to regenerate the files by doing the following: Open your current Firefox settings (AKA Firefox profile) folder using either * "3-bar" menu button > "?" button > Troubleshooting Information * (menu bar) Help > Troubleshooting Information * type or paste about:support in the address bar and press Enter In the first table on the page, click the "Show Folder" button. This should launch a new window listing various files and folders in Windows Explorer. Leaving that window open, switch back to Firefox and Exit, either: * "3-bar" menu button > "power" button * (menu bar) File > Exit Pause while Firefox finishes its cleanup, then rename any of these files that you find: * '''compatibility.ini''' to something like compatibility-old.ini * '''extensions.ini''' to something like extensions-old.ini * '''extensions.json''' to something like extensions-old.json * '''extensions.sqlite''' to something like extensions-old.sqlite (might not exist depending on how long you've been using this settings folder) When you start Firefox back up again, it should explore your profile folder and other folders to rebuild the list. It probably will ask you to approve some of the extensions. Once things settle down, could you check the Add-ons page again. Any improvement?