There was a power outage in my area which lasted a couple of hours. My Home Theater System was on when power went out. When power was restored, my Yamaha RX-V800 has no sound coming from the MAIN speakers. Sound does come from the center, rears and subwoofer. Only the MAINS have no sound (this was discovered by running the test tone). What could be the problm here? P.S. I went throught the menu several times and can't find anything wrong.