This error popped up a while ago while closing an explorer window. The explorer window had gone before the msg appeared. I thought the desktop would probably go bye byes when I clicked OK, so shut down other apps first. When I clicked OK, the msg just disappeared and everything seemed OK. I started a few non-critical apps and did a little browsing thru folders and the net without obvious problems. Then I rebooted, before getting back to more serious stuff. Haven't had any recurrences, so far.
Any clues? I had a hunt on Google on MSKB but didn't see anything useful.