I have a Sony SAT-A4 Directv Tuner, and every once in a while, there is no audio on certain channels. It only occurs on channels broadcast in Dolby Digital, and mostly on STARZ and SHOW (channel 543). I know it's not my pre/pro - it's been tested. I've also called Directv, and they say it's not them. So, I guess, it must be a problem with my SAT-A4? I'm wondering if anyone else has experienced this problem before. Thanks!