I've been reorganizing my folders, and while working on this, I will occasionally find that I can no longer create a new folder or rename an existing one, or, somewhat worse, when I rename a folder, it will disappear, along with the messages that were in it. The messages that were in the missing folder don't show up in a search, and aren't in trash. If I close Tbird and quickfilters, and sometimes also restart the computer, the functions again work as they should (but the missing folders do not reappear). Rebuilding the parent folder doesn't recover the missing subfolder. The problem can happen when Tbird is the only open application. Any idea what can cause this? Or where the missing emails might be? Thanks Kent