Start *Windows'* safe mode with networking enabled - win10 http://windows.microsoft.com/en-us/windows-10/change-startup-settings-in-windows-10

Still In Windows safe mode, start thunderbird in safe mode - http://support.mozillamessaging.com/en-US/kb/safe-mode

Does problem go away? Please reply to let us know results.

Didn't help, but thanks for the suggestion. It seems to happen most when filters are being run on folders.

just how many filter do you have?

Matt said

just how many filter do you have?

I have 40 local folders that I filter to. This is also happening when I run "Delete mail marked as Junk from folder" from the tools menu. (I get a lot of Junk).

FYI - This is on a laptop that always has Thunderbird, Chrome, and EditPad running.

How many messages currently in your Junk and Trash folders?

Wayne Mery said

How many messages currently in your Junk and Trash folders?

I empty them at least twice a day. Sometimes as many as 50 in each.

BTW- When I tried FireFox I had the same type of problem so I went back to Chrome.

Your combination of test results suggests something related to Windows 10 or Antivirus (despite your results with safe mode - which I'm not sure I trust).

Did this machine previously run windows 8? What happens if you reinstall thunderbird from http://getthunderbird.com/ ?

Wayne Mery said

Your combination of test results suggests something related to Windows 10 or Antivirus (despite your results with safe mode - which I'm not sure I trust). Did this machine previously run windows 8? What happens if you reinstall thunderbird from http://getthunderbird.com/ ?

Yes, this was a windows 8 machine. I had problems with thunderbird even on 8. Very often clicking on links didn't work. I recently upgraded my Thunderbird version because of this problem. I'm going to uninstall and reinstall after downloading from http://getthunderbird.com/. I'll let you know what the results are.

I can't uninstall thru Control Panel, don't know why. I've rebooted the machine and uninstalled other programs thru the control panel.

Never any need to uninstall first.

But what you could do is delete the Thunderbird program folder, then install.

I deleted the Thunderbird program folder, defragged the drive, reinstalled thunderbird, and still have the same problem. I've run 3 different antivirus programs and they all come back clean. I have no idea what to do next.