If you're sure that the receiver has gone south and that it's not a setting that got screwed up, then I'd suggest one of the following (to perhaps somewhat increase the daily joy of your gamer):
1. Try using an adapter cable (like
this one) to combine both component video sources into one, and then connect that one into the working input on your receiver. This approach only works if you only have one of the sources on at a time. It is, however, completely passive and requires no additional switching on your part.
2. Get a component video switch, like
this one. This requires you to switch the video on this unit, but you can have both sources on at one time.
The linked products are just example products for the approaches that I suggest.
Adam