Thunderbird 102.9.0 hangs (Ubuntu linux 22.04)

Hello. For the last week or so, Thunderbird has become unusable for me. Shortly after doing anything, such as clicking on a message, it hangs and I can get nothing else done. If I go to another window, and then back to thunderbird, it redraws the window frame, but with transparent window contents (the underlying screen is visible). My "top" linux command shows that thunderbird is eating 100% CPU (on only one thread of the multithreaded 12th Gen core i7). I've looked at the Activity Manager before the freezing, and nothing untoward is reported. After the freeze, Activity just opens as another transparent window, so I don't know if anything is happening. I tried resetting the global index as was suggested in another post here. It indexed all my boxes without any error but was not changed afterwards. I'd really appreciate suggestions here. I'm not aware of having done anything such as a change of settings, so it has me beaten at the moment. I've been using Thunderbird for years without seeing this before. Kenneth.