Background/Explanation: I've been doing some disk housekeeping: deleting files, moving them around on external drives, etc. I somehow ended up with a copy of the Desktop DB file in the Trash. The file wasn't visible, but whenever I emptied the Trash, I got the annoying message The operation cannot be completed because the item Desktop DB is in use."
After clicking Continue, the Trash icon reverted to its apparently empty state, but the next time I put something in it and went to delete it, the same message appeared. I dropped to Terminal and thought I would just delete the file there, but it wasn't there. So I simply ran:
$ rm -rf ~/.Trash/
mkdir ~/.Trash/
Thinking that would solve the problem, and it did.
Except that the Finder was smart enough to tell that the ~/.Trash folder had been deleted, but not smart enough to tell that a new one had been created. So when I tried to drag a file there, I was told The file WHATEVER will be deleted immediately, continue?. I had to restart Finder (Option click-and-hold on its dock icon) to get it to work again.
[robg adds: I'm not sure I can explain why the Desktop DB file wouldn't have been visible. If you manually recreate your trash, you might also want to run chmod go= ~/.Trash, to remove all permissions from group and others. That will match the stock permissions on that folder. I'm not sure if Repair Permissions would catch this one or not.]

