Did you get into the Call of Duty 4 beta? Did you get in by having a buddy exploit a glitch that allowed people who did not receive keys from Infinity Ward to download the beta?
If so, BANNED!!! You are now banned
forever for a day. Wait, that's not so bad, but let this be a lesson to you! Don't glitch the system.
Hit the cut for Microsoft's statement on the matter and some beta gameplay that should hold you over while you take a 24 "break" from Live.
Microsoft had this to say:
Now enjoy some footage of the beta you aren't playing.