You probably need to disable anti virus scanning of email, or even place an exemption for the Thunderbird process in the product.

Nope, didn't do it. :( As I said, this just started the other day when I d/l and installed the latest update to Thunderbird. I've never had this problem before, and have had the same virus scanner for years. If I could figure out how to back out this update/uninstall it that's what I'd do. Y'know, uninstall & reinstall. Guess I'll be doing some looking around. *shrug*

Thanks for the try, appreciate it!

To diagnose problems with Thunderbird, try one of the following:

• Restart Thunderbird with add-ons disabled (Thunderbird Safe Mode). On the Help menu, click on "Restart with Add-ons Disabled". If Thunderbird works like normal, there is an Add-on or Theme interfering with normal operations. You will need to re-enable add-ons one at a time until you locate the offender.
• Restart the operating system in safe mode with Networking. This loads only the very basics needed to start your computer while enabling an Internet connection. Click on your operating system for instructions on how to start in safe mode: Windows 10, Windows 8, Windows 7, Windows Vista, Windows XP, OSX

If safe mode for the operating system fixes the issue, there's other software in your computer that's causing problems. Possibilities include but not limited to: AV scanning, virus/malware, background downloads such as program updates.

Thanks again for the help. I was in the midst of doing just that when another update came down. That update solved the problem.