I've had this problem for many many years ! I FINALLY was able to capture the error message. Approximately 50% of the time, Thunderbird COMPLETELY hangs when returning from hibernation, can't close it in anyway except to use the Windows taskbar to close it (or of course kill task in task manager). It seems to be always related to calendar script. Note this is Sept 1st. Is there a way to deactivate calendar ??? I never use it. "A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can continue to see if the script will complete. Script: chrome://calendar/content/widgets/calendar-minimonth.js:564 " My system : OS Name Microsoft Windows 10 Home, Version 10.0.19044 Build 19044 Thunderbird Version 78.11.0, Build ID 20210528153351 Same problem as https://support.mozilla.org/en-US/questions/1366804 Quote : " ukpolyboy 2/4/22, 1:39 AM Ever since upgrading to windows 11 when I hibernate with Thunderbird active, on return it will never get any new messages. Closing and reopening fixes this but this is annoying and never used to happen. Any solutions? " COMPLETELY hangs after returning from hibernate