I've had more than a few problems myself. One quick fix I found when I'm disconnected while playing, is to press start, go to Multiplayer, then press Y (I think it was Y...). This should reconnect you.
i dont even play muiltiplayer but i do know that every now and again ill get a message pop up on screen saying ive been disconnected from xbox live, whilst playing this game. and only this game. --- GT : DeadJericho / PSN : Focalpoint / Correct terminology is 'Could NOT care less'. Learn English!