My Yamaha DSP750 appears to have died. I can not get any sound out of any of the digital feeds, both DVD via coax and TV via optical are dead. Analogue like CD and multi-channel in work fine and all video feeds seem fine. I have tried re-assigning the coax inputs but still no sound. The wife claims all she did was change TV channel on the Netgem box and the sound stopped. Any advice, or should I take the wife back and ask for a refund.