I am experiencing severe audio dropouts on my HR20 on some of the new National HD channels where my AV receiver indicates that the show is recorded in Dolby Digital. Specifically, I get an audio dropout randomly but on average about every 15 seconds. When I hit the "Backspace/Replay" button, however, the audio that had dropped out, now plays just fine. So the DVR is recording the audio, but the dropouts occur on original playback. I've tried a menu reset with no change in the issue. I have seen suggestions to check the signal strength on 103(b). My signals are routinely in the mid 70s to mid 80s on both tuners. Is this sufficient or should I have DTV come out and realign??? Thanks.