Hi, Certain Firefox problems can be solved by performing a ''Clean reinstall''. This means you remove Firefox program files and then reinstall Firefox. Please follow these steps: '''Note:''' You might want to print these steps or view them in another browser. #Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer. #After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu). #Delete the Firefox installation folder, which is located in one of these locations, by default: #*'''Windows:''' #**C:\Program Files\Mozilla Firefox #**C:\Program Files (x86)\Mozilla Firefox #*'''Mac:''' Delete Firefox from the Applications folder. #*'''Linux:''' If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see [[Installing Firefox on Linux]]. If you downloaded and installed the binary package from the [http://www.mozilla.org/firefox#desktop Firefox download page], simply remove the folder ''firefox'' in your home directory. #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. More information about reinstalling Firefox can be found [https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems?esab=a&s=troubleshooting&r=3&as=s#w_5-reinstall-firefox here]. <b>WARNING:</b> Do not run Firefox's uninstaller or use a third party remover as part of this process, because that could permanently delete your Firefox data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. <u>These cannot be recovered unless they have been backed up to an external device!</u> ---- You must create a new profile in order to use it. *https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles Also, you can copy over your bookmarks and stuff but be careful not to copy over corrupt files. *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

You need to delete the profiles.ini file as well because Firefox registers all profiles that you see in the Profile Manager in this file and deleting the file on disk causes Firefox to display this error message. *http://kb.mozillazine.org/profiles.ini_file Otherwise you would have to use the Profile Manager to create a new profile. *https://support.mozilla.org/kb/Managing+profiles