I was just looking for the same answer...
Sadly, it looks as though the only answer to any VUM problem is re-install... uninstall (erase), and start over. I see nothing in the GUI to reverse an import, remove a patch from the database, or even get the stupid thing to download patches it's missed (something that happens every d*** time I go to install patches.)
The only other option is to mess with the database directly. That's obviously the next to last resort -- backup the db, or be prepared to reinstall.