I would not rule out an overheating problem. Are you suggesting that your receiver High temp is higher than 138°?
Forget the Low and Average reading, the High temp is what is killing these receivers. There is a long thread here of 99 pages and I cannot recall anyone say that his receiver runs without any problems at higher temp than 138°. Just to make it clear, the HD is not the hottest device on this receiver, the HD has a temp sensor built in and Dish is simply using this sensor reading. My 722 shuts down @ 138°, I added an exhaust fan and never had any problems since.
The only problem with the High temp reading is that even if you lower the receiver temperature significantly, the High temp reading is not being updated. I posted several questions to Dish and no one can tell me how to reset this reading. Unplugging the receiver for an hour or so will reset the Low and Average reading but not the High reading.
