For the past week or so, I've been getting the following message every time I open Thunderbird. "The folder 'Outbox on Local Folders' could not be compacted because writing to folder failed. Verify that you have enough disk space, and that you have write privileges to the file system, then try again." Also, the folders appear to be empty, but the eventually repopulate. I have plenty of disk space and haven't changed write privileges. A Google search doesn't turn up any solutions. Can anyone help?