Try Thunderbird in safe mode. This may be related to an add-on.

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

This did nothing--same error message and program does not open.

Can you confirm you did start Thunderbird in safe mode?

I started Thunderbird with the "shift" key held down, as described in the help section. If there is another way, I don't know about it. Program will not open--just the error message.

Shift key does nothing here either. Try these instructions instead and use "Start -> Run". http://kb.mozillazine.org/Safe_mode#Windows