Go to [http://kb.mozillazine.org/About:config about:config] and find '''plugins.update.notifyUser''' and make it FALSE by double-click on it. thank you Please mark "Solved" the answer that really solve the problem, to help others with a similar problem.

There is well worth it

Try: *http://kb.mozillazine.org/Preferences_not_saved *https://support.mozilla.org/kb/Preferences+are+not+saved You can also try to reset the extensions registry file, 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, not compatible, extensions in "Tools > Add-ons > Extensions" then click the Tools button at the left side of the Search Bar (or click the "Find Updates" button in older Firefox versions) to check if there is a compatibility update available. ---- Create a new profile as a test to check if your current profile is causing the problems. See "Basic Troubleshooting: Make a new profile": *https://support.mozilla.org/kb/Basic+Troubleshooting#w_8-make-a-new-profile There may be extensions and plugins installed by default in a new profile, so check that in "Tools > Add-ons > Extensions & Plugins" in case there are still problems. If the new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files. See: *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox