try right clicking the folder and selecting properties and then the repair button.

Hi Mark, this deleted all my emails in the target folders and still didn't fix the problem. I can't even delete them to start over..not to mention all the emails are deleted now. Unless by some universal irony they all appear back in their spots tomorrow - LOL - I've lost a lot of needed messages - hence the reason I created folders for them. :( Got anything else that might work? The messages are gone so can't cry about it, but do need to fix the problem in case it happens to more folders. So anyway the folders are imap'ed so they are on the thunderbird site. The folders that are local are ok so far.

Matt - my apologies - was chatting with a guy named Mark for the ABCmouse problem - confused the names. :(

Repair only rebuilds the index of the folder. That Thunderbird can not build an index is something of a worry. Normally I would point the finger at corruption. But this time I don't think so.

Best to go back to basics here I think.

Have you rebooted your computer? Tried windows safe mode with networking?

My guess is something is locking the physical file that contains the folder mail. A reboot my release whatever it is if your not in the practice of regular cold starts.

Either way failing that Windows safe mode with networking should see the file freed up if you start Thunderbird while in safe mode.