Marcus, it's time to call the factory for the default procedure. You might give it a try, but I doubt that the AVR is like a SLC503, with a battery and short cap procedure.
The configuration settings,speaker settings,individual volumes,size,etc. are stored on a chipset and will remain even if the receiver is unplugged and not in use for a long period of time. Try the master reset, look in owners manual for this. It is usually just a matter of pressing and holding a couple of buttons. If this does not work consult an authorized repair center.