Hi Dave, sorry to hear about this problem. Was that the only data you lost -- bookmarks, history, and settings were all okay?

Sometimes when the browser thinks there is a problem with the profile, it will create a new one. Look on your desktop. Do you see a folder called; '''Old Firefox?''' Look inside. Look for the folder with the latest creation date. https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update