is it also there when you play a cd or something with a source that isn't your dvd player or tv?

if so, check the 'problem sources' seperately, turn on your tv, not your dvd player and turn on the receiver, is the high pitch sound there then? then turn off the tv again and turn on the dvd player, is the high pitch sound there? I've been thinking about electronic 'noise' generated by your tv, and then picked up by your audio interconnects...