I have a SA HD8000 box.
When I watch live TV which has Dolby 5.1 or even just Stereo sound through my Onkyo 780, every 5 or 6 seconds there is an interruption of the sound, like someone is disconnecting and then reconnecting the wire to the back of the box. Typical TV with PCM is okay though, no problems.
But, when I playback Dolby 5.1 or Stereo from the DVR, the sound is perfect.
I've had the Home Theater receiver for about 2 weeks, it worked fine in the beginning and I don't know if something is wrong with it, or the cable box or the cable company.