Please - start Thunderbird in safe mode

 https://support.mozilla.org/en-US/kb/safe-mode

- go to tools | addons - remove the lightning addon - restart - start thunderbird - if you need the lightning addon, add it back at tools | addons

Does that help?

I don't have the Lightning addon loaded to begin with? So it's not there for me to remove. I did start Thunderbird in safe mode and was able to get it to work this evening. Tomorrow I'll try starting thunberbird in regular mode again. Is there any solve beside removing the lightning addon?

Please post the full list of addons, both enableld and disabled, from Help | Troubleshooting

I don't have any add ons listed as installed!

Here's the weird thing. I opened TB in safe mode. And even though I did not have any add ons ... I pretended I had the lightning add on, So...I just made sure it was not installed. I restarted the computer the next day, opened TB and it seems to be working properly for now.

Pretty interesting.

Please go to Help | Troubleshooting | Profile Folder: Show Folder | pick the extensions directory

Can you post a screen shot here please.

https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem

Here's a screen shot

sorry. need you to actually go into the extensions directory :)

Here's the extensions directory folder contents

So actually, you went one directory level too deep.

But it's OK, your shot does show that Lightning/calendar was installed at one point. Which very well could have caused your problem.

OK! Thanks for the help. I think lightning calendar is now not installed...I'll monitor for a few days and open a new question if things go bad! I've had a bad week with Mozilla products. I also use Firefox and lost all my bookmarks...only to find I can retrieve them thru Sync...which I did. Fingers crossed all will remain OK.