saw your post on my thread for the WAW modders. sorry to say we pretty much have no options, you can call up activision or trey support but all they offer is an email detailing why they cant fix the problem. lots of people have this happen because of the modders, but all activision does is ask you for their gamertag (assuming you still have it in your gaming history, and hardly ever play XBL..)
i have tried getting friends to invite me to zombie XBL lobbies, but it is still corrupted. it just sucks that joining one game with cheaters, gives the honest gamer a negative 3420791238412379472834 XP and no way of joining any online matches. i would say you could atleast let support know that you got screwed over, one more person they know is pissed about their lack of patches/help.