If I were you I'd send a nice note to the Dean and let them know how disappointed you were and how great there school is blah blah blah, and probe them for what would make your app stronger in the future.
In other words, elicit out of them why the rejection. I don't know if it would bear fruit, but it would be worth a try. Who knows - maybe they'll take it as a sign of serious interest and reconsider.
C2