Jim, do you have any extensions in TB? Have you tried running TB in it's Safe mode to see if that helps?
http://kb.mozillazine.org/Safe_Mode9 times out of 10, a new Profile will help, but if you can't answer some basic questions, you probably won't get help anywhere.
We don't have access to your machine so we have to take time to ask you questions because not all machines are set up the same way.
Have you tried disabling NIS before downloading emails?
I'm not going to object to you wanting to close. Just trying to help.