I have a 2 year old AVR-391. Over time it has had strange bouts of what I call "alien chatter" where the unit starts giving me a strange alien like sounding audio signal through my speakers when I would power it on or change a channel ocassionally. Now I have a strange high pitch resinance that is coming through the front left surround speaker. I have changed all HDMI cables, speaker wires, swapped rear speakers to the front and no change. Does anyone know what can do for this aside from replacing the entire unit?