I personally believe that there is a direct connection between HDMI board failure and heat when it comes to video issues with these late generation AV receivers. A few months ago I got a call from one of my friends telling me his Denon AV video had stopped working. I went over to his house only to discover that the receiver was crammed in to a cabinet with no ventilation what so ever! Upon opening the cabinet I was met with a blast of heat that would compare to decent space heater! The receiver was so hot you just about couldn't touch it.
My own experience with the issue was when I put my Onkyo receiver in the downstairs family room. I have a wall unit and the receiver is located on a shelf in the bottom cabinet. There are glass doors which I must leave open while in use. I also added a small fan to circulate air out of the back of the cabinet. Every once in a while my wife will forget and close the doors at which point I will start having issues with the video freezing which requires the receiver to be switched off and back on to get it to work again. Open the doors and the problem resolves itself.
I think many times we forget about the fact that these things generate a lot of heat that needs to escape the chassis. Putting your receiver in a cabinet, stacking equipment on top of it, or placing on a shelf without proper clearance are all asking for trouble.
