I can't delete a recently imported clip until background processes are complete…

When I attempt to delete a clip I just imported (20 minutes long) FCP X tells me it will be moced to trash as last reference to it is being removed. Then I get the error message pasted below:

Background Tasks Running

This action cannot be performed while background tasks are running. Try again when background tasks have finished processing or after canceling them.

Short of quiting FCP X and deleting the file in Finder what am I supposed to do to stop all the background tasks? Presumably these bkgd tasks are analysing footage and audio and generating thumbnails etc.