My Xbox has a problem too...
I log in to my account, then I start COD: Black Ops II.
It starts... got Blackscreen.
Xbox freezes while Blackscreen.
I need to restart it by hand.
And that is everytime I start Blops 2.
Black Ops 1, Modern Warfare 2, Battlefield 3 and Minecraft work perfectly without freezes.
If I don't log in to my account and play with Player 1, I can play campaign and zombies, but still not Multiplayer, if I start Multiplayer it freezes and I need to restart the Xbox by hand.
BTW: Default starting for BO2 is Multiplayer.
edit: Fifa 13 works too.