I am having a problem similar to that reported by the original poster, mine is a bit different but unfortunately I am not allowed to make a new thread since I'm just a newbie
This is the second time this has happened with my SA8300HD:
I have problems with live television on every digital channel, I can watch for about 10 seconds and then the audio and video will freeze for about 5 seconds then start again. After another ten seconds it will freeze again and the behaviour continues. I have the same problem with playback of recorded shows. This sounds a lot like the OP's problem however I also hear an audible 'click' (fairly loud, hear it from across the room) every 10 minutes or so coming from the 8300HD. The 'click' happens if the unit is on or off. If the unit is powered off and I put my ear to it it sounds to me like the hard drive is seeking constantly (doesn't stop even after the unit has been switched off for a long period).
Interestingly, I can watch analog channels with no problems (still hear clicking from time to time).
I have tried rebooting several times by unplugging for several seconds and then plugging back in. This doesnt fix the problem. I also tried reauthorizing my terminal but this did nothing as I expected.
Last time this happened (about 3 weeks ago) I worked on it all evening and nothing worked, I expected I would have to exchange the unit the next day. However, when I woke up the next morning it was back to normal. I think I read somewhere that the unit downloads software updates around midnight? Maybe this fixed things??
Anyway, just wondering if anyone else has experienced this or better yet has a fix for it.