Problem with Mitsubishi M-VR800 Audio Receiver - Repairable?

[Patriot]

I have a Mitsubishi M-VR800 receiver. The problem i'm having (and it seems some other owners of this receiver have had the same problem) is when the receiver is first turned on, it insists on going to input 4, and says on the display "decoder". When I push the buttons for the other inputs (CD/FM, etc) it will briefly switch to that input, but then change back to the DECODER input.

After about 10 to 15 minutes or so, the receiver will stay on the input of my choice, and play just fine, but periodically switch back to input 4 and display "decoder". It seems that after a while of playing, it will begin to switch back to input 4 more frequently.

If I hold the button for the input of my choice, it will stay on that input and play, but I worry this is leaving some switch open and will burn something out.

If I hook up a music source to input 4, it will play when the machine automatically switches to "decoder", albeit with a much decreased s/n ratio. If the s/n ratio wasnt so much poorer, i'd be fine leaving it how it is, as the music comes through.

Google turns up nothing other than people have had the same problem with this receiver, but i've found no solutions. Any ideas?