What is your anti-virus software?

Norton internet security

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?

hi. that does work, but what about when I go back into normal mode...I will try and see, and let you know.

Chances are that Norton is causing the problems with Thunderbird. Exclude the Thunderbird profile folder from being scanned by Norton. Don't let Norton scan incoming and outgoing messages or attachments.

hi. I disabled Norton, and it still happens. I have also excluded it too. I am able to delete a few messages, then it freezes, sometimes the bottom green "thinking bar" is active, and then I cannot select any other emails to read either. the only way out is exit thunderbird, restart, but it happens again after a few deletions...

I have no idea about Norton. You might ask in a Norton forum for help. Do you run any other 'security' software?