My TV is a Panasonic TC-L58E60, and my cable box is a Pace RNG2000N Dallas. My problem, I believe, seems to be when the resolution of the output from the cable box changes. If I change channels between 1080i channels, or between 720p channels, or between 480i channels, there's no lag. But if I change, from, say, NBC over to Fox, there's about a 30 second delay. I can't set the box to a set output, such as 720p, as I've seen suggested around the forums. My audio options from my box are "TV Speakers," "Stereo" and "Advanced." If I choose Stereo, it's so super quiet I can't hear anything, so I go with Advanced, which gives more audio options. I have compression set to heavy and have tried stereo output set to both "stereo" and "matrix." I tried the Surround Sound beta option under troubleshooting on the Xbox, but I could hardly hear anything on channels like Fox and NBC
I also get a lot of audio sync issues. Watching an Amazon instant video last night, the sound was lagging just enough to be annoying. Watching a basketball game from the DVR yesterday, you'd hear the basketball hit the ground right about when it was back up in the players hand.