I am anticipating some users may end up accidentally breaking their extensions trying to go back to Firefox 3.6 after trying out Firefox 4.0. The method below also solves pretty much any add-ons installation issues.
Firefox will automatically disable any extension that is not compatible with build you are running. This will happen if you try to go back to an older (Firefox 3.6) version after already running the same profile in a newer version (4.0) of Firefox. However, even after you return to the correct version of Firefox, it will not automatically re-enable the disabled add-ons for you. The good news is you shouldn’t have to go through and reinstall all your extensions. In order to re-enabled your add-ons follow these directions:
- Close Firefox
- Locate your profile folder
- Delete the following files from your profile folder and restart Firefox:
Firefox will rebuild your extensions and themes list and these files. Your extension should be re-enabled and functioning again after the restart.