First, sorry for my english. The same shit happen to me. BUT even weirder situation. I got Halo 4 same time as OP, maybe later, played on my office console. I have gamertag on USB stick. Later I went home and put stick in home console, went on Live, checked what is going on and that's it. Few days later I saw this thread on neogaf and checked my account and everything was fine. Went to friend's house and we played Reach over 8hrs in multiplayer. Everything was fine. At home didn't played nor turn on console at all, I had other things to do.
In morning of 6th November I received email from Live enforcement team that my gamertag is banned. Why? First I twitted to MS support cause they are great guys and nobody replied to me. Great. I searched and found out that they don't TALK AT ALL ABOUT BANS. It's company policy to not talk about that via support or something like that. I called them and they gave me forum address to complain there. I posted my issue. They deleted thread and said that they are sorry and they understand, but ban will stay because of PRE RELEASE GAMEPLAY. I wrote another thread, they deleted and said how this is not place for this kind of talk. I had on my gamertag 1650 msp, dozen XBLA games, lot of DLCs, even fuckin' BF3 server. What kind of pirate invest in online?
After week of useless writings and talks with MS I turned on my home console and wanted to make new gamertag and play some Halo 4 with friends. When console tried to connect to XBL error appear and after testing connection Console Ban message popped up. What? I EVEN DIDN'T PLAYED HALO 4 ON THAT CONSOLE!!! I wrote again and they repeated their stance about not discussing bans.
Now, I play lot of games earlier cause I'm writing reviews from time to time and never had issue with publishers. I don't have any MS PR contacts cause they are not supporting part of Europe where I live, but SE, Activison, THQ and others sending me copies. So, obviously their banning system isn't perfect and they don't want to acknowledge that.
I didn't want to open new thread when this happened to me, but seeing now that this issue can't be solved I wanted to share my story.