try disabling your antivirus program, they are good at causing that sort of error.

Sadly, no change but thanks for the suggestion.

I see others have had similar problems but with an earlier version. I have the exact same version as the girlfriend but I'm on w11. I had this same issue a few months ago but can't remember how I resolved it.

Anyone else have any suggestions?

A simple option is to check webmail for a corrupted message:

https://support.mozilla.org/en-US/questions/1301414