Thunderbird crashes on startup - Mac

[elrich]

Thunderbird has been functioning fine for me mostly, and then today it refuses to start up. I'm wondering if I caused this problem.

When I was starting up my Mac today, I noticed it hadn't started up (I generally have my Mac remember which apps were open previously and open them all automatically -- which can take 5-10 minutes).

But when I looked again, it still wasn't open and I wondered if I hadn't clicked directly on it. So I clicked on it in the Dock again. Then I got two simultaneous dialog boxes -- one said that Thunderbird was trying to install something, and the other said that I already had a copy of Thunderbird running and couldn't start another one.

I backed out of all that, and now every time I start Thunderbird, it crashes and gives me the crash dialog box (send crash report to Mozilla, etc).

I tried reinstalling, but it didn't help.

What can I do?

[elrich]

P.S. I'm running Thunderbird 52.2.1 on Mac OS X El Capitan 10.11.6.

[DanRaisch]

Does the same thing occur if you launch the application in Mozilla Safe Mode? http://kb.mozillazine.org/Safe_mode