Forgot to mention...I downloaded a file, on the recommendation of a colleague, that included malware. My virus protection flagged it immediately and was supposed to "remove the threat", but I have been experiencing problems with FireFox, too. Not sure which problem may have contributed to the other.

What is your anti-virus software?

AVG...licensed, not the free version

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?

LONG day at work today. I'll give it a try tomorrow. I'll let you know how it goes. Thanks for the suggestions!

Yes! While working in safe mode for both Windows 7 and Thunderbird, I haven't experienced one problem. So...what does that indicate, and how do I fix it?

It indicates your anti virus (or other resident program) is the cause of your issue.

AV programs get the most press, as they are most common. But they are not alone. .Run MsConfig by typing it into the start menu search box and try disabling some of the startup items in the startup tab. I would start with anything AVG as your computer will still work without it. Because MsConfig is point and click it is simple to reboot and change settings, making it quite a good diagnostic tool. Google anything you do not know in the list as you may still have a malware issue in your startup.

Thanks! Will give it a try and let you know. Appreciate the help!!