Try to start *Windows* in safe mode with networking enabled.

- Win8 http://windows.microsoft.com/en-US/windows-8/windows-startup-settings-including-safe-mode

- Win7 http://windows.microsoft.com/en-US/windows7/Start-your-computer-in-safe-mode

- XP http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/boot_failsafe.mspx

Still in Windows safe mode, start Thunderbird in safe mode.

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

Does the problem go away?

gsmarble said

I always leave Thunderbird open when I'm on my computer working so that I can catch emails as they come in. There were a lot of windows updates to download this morning, and a Thunderbird update, also. I started downloading the Windows updates and continued with my business. I do not remember if all the updates had installed when this happened since I was in another program, but I noticed an email alert popped up from the system tray. At that time I couldn't do a thing. My entire computer locked up. I let it sit for about 5 minutes thinking that it was just slow, but it never unlocked so I had to hot boot my computer. When the computer came back up I saw that all the windows updates had installed. I brought up Thunderbird so I could check my email. I went ahead and updated Thunderbird (since it had alerted me when it started that the update was ready), and continued with my business. As soon as I got another email, the whole system locked up again. I rebooted again. I then got back into Thunderbird and it was the ONLY program running and opened on my desktop. I got an email alert in my system tray and the whole computer locked up again. I'm afraid to open Thunderbird anymore, but need my emails. Can I disable the system tray alerts?

I'm not sure what really solved the problem. I received more updates for Windows and the problem resolved itself. Apparently it was a Windows problem and not a Mozilla issue.