The first thing to check for something like that is stray strands of wire at the receiver. Disconnect and reconnect each wire. It generally doesn't take a lot to short you out, and if left that way, could cause damage, which is why the receiver shuts off. If that isn't it, move next to the speakers and check for strays as well as a consistent and correct hook up for + and - from the receiver. If that doesn't fix it, disconnect all speakers and hook them up one at a time to see if it is isolated to one speaker (the in ceiling ones in particular).