I installed the TBSync add on and it seems to have corrupted the Lightning add on. Thunderbird just hangs and keeps showing the attached image. I removed the TBSync add on but the problem persists, completing locking up Thunderbird. The only way I was able to salvage it was to remove the lightning add on entirely (at which point Thunderbird starts working normally again). I tried this solution to no effect: https://support.mozilla.org/en-US/questions/1226335#answer-1134855 Then I tried re-adding the lightning add on and the problem comes right back. How can I completely "reset" lightning so it starts working normally again? Note: I had set up a connection to iCloud within Lightning. When I setup TBSync, I used the same application password from Apple for TBSync that I had used to setup a calendar in Lightning. My guess is this may be part or all of the problem. If so, I do need a way to delete all Lightning prefs and maybe that will help. Thanks!