Audio/video scrambled - DirecTV

I have a Directv HD DVR Genie. Within 1 hour of turning on the equipment, the audio and video signals are scrambled by high frequency noise and video static. After a few seconds, the receiver and TV shut down, then turn back on automatically, and programming continues as thought nothing had happened. This problem recurs with greater frequency, the longer the equipment is left on. This suggests to me that there might be a problem with over heating; but there is pleny of ventilation around the receiver. A call to Directv Tech Support was unable to confirm my suspicion of overheating or to provide a solution to resolve the issue. Any suggestions form the community will be greatly appreciated.

This question, "Audio/video scrambled," is about DirecTV channels, programming, equipment, and sports.