Can you access Preferences in safe/troubleshoot mode (hold Shift when launching TB)? Do you have any language packs?

Thanks so much for that. I can easily access Preferences now using safe/troubleshoot mode as you suggest, and I have fixed the *.pdf problem. However, now when I launch TB normally I still get that "not responding" message coming up when trying to access Preferences, such that ultimately I have to close TB as best I can. So there is still a bug??

I have a language pack ENG GB Lang Pack.

Safe mode disables add-ons, uses a default layout and disables hardware acceleration, among other things. Start by disabling or removing the language pack, then restart in normal mode. If the problem remains, disable hardware acceleration in Preferences/General/Indexing, then restart in normal mode. If the problem remains, and you have other extensions, enable them one by one until you find one that's incompatible.

Thanks for that quick response. This is how it panned out. I removed the English Language Pack and started TB normally and it worked without the "not responding" for preferences, in effect was normal. Tried downloading and reinstalling the English Langauge Pack and TB went back to "not responding" routine.

So I've removed the English Language Pack again - would like TB to operate in GB English - have you any suggestions??

Again thanks so much for what you've done. I am just an elderly (73) user and just want to do e-mails easily. This problem only started when I updated to TB versions 91....

Download and run the English (British) installer over your existing TB:

https://www.thunderbird.net/en-US/thunderbird/all/#E

If you need to operate TB in additional languages, let's hope the issue with language packs is fixed in a future release.