I did some further testing yesterday. I bought a Oppo 970HD yesterday to rule out it was my DVD player, plus I wanted its extra features.
I let the receiver run most of the day with cable and left the PS3 on. After several hours I started switching between DVD, DTV and CBL/SAT, sure enough the picture started to drop. Something that was new though was that with the Oppo it kept trying to show the picture and it would flash every 30 seconds or so and show a picture then go back out.
Next, I put a fan right next to the receiver and blowing on it. Once I did this, I never lost picture. Even before the fan, there is plenty of air flow around the reciever and nothing on top, but it still felt quite warm.
I'm leaving it on again today with the fan and I'll see if I can get it to go. If not, this can only lead me to an over heating issue. I suppose I could order a cooling system to resolve the issue for good (assuming it doesn't go out today). Still not good that the reciever can't cool itself enough alone, but at least I might be able to get it to work.
I will report back once this "test case" is complete.