Avr 4800 all of a sudden no sound out....

the unit was fine yesterday morning...now no sound out on any level or function..ie dvd/tuner/tv...what gives? I tried unplugging and replugging still no go is there a "reset" button/switch? someone , anyone please help.The set up is as such I run a Denon 5 disc dvd in, a vcr in, a hdtv cablebox in and a Kenwood 6 +1 cd player and an addl Kenwood recv in...(hardly use that except at Holidays). All was working fine like I said.
Thanks,
Geoff