Disconnect speaker wires AT the receiver and try that. If it still kicks off, it needs to be fixed. Are there any bad smells? Any dimming lights or humming from the piece?
IF the problem goes away with the speaker wires disconnected, check 'em out thoroughly. And I do mean every inch. Look for pinches in the wire or bad connections at either end. A SINGLE strand of wire crossing to the other side can do as you describe.
Do you have any way to check the speakers? Maybe where you bought them? Were you using the 'free' speaker wire that sometimes comes with box speakers? How long has the receiver been unused?