Ahh, I've experienced this before. Cover one of the magnets (or piece of metal on the door?) with a piece of tape. If that isn't enough, try a few layers of tape, and adjust the position if necessary (if the thickness of the tape becomes and issue).

Another idea is to move the magnets so that they don't meet completely flush. For instance, raise the one on the cabinet itself some distance so that when the door is closed, only the lower half of that magnet is touching the magnet (or metal plate) on the door.