Are there any fluorescent lights along the path of the wiring? Like near a kitchen or bathroom, maybe? I read somewhere that fluorescent lights emit a signal that messes with computer wiring, like ethernet cables. I'm not sure if this is the problem or not, but we usually get to solutions by crossing off the list everything that isn't causing the problem. That's about the only thing I can think of (externally), though you may want to check the system settings of the 360 to make sure there's a valid Live account (meaning that the suscription didn't expire) and that all the internet settings are good.