We just got out DirecTV installed this week. They installed a HR24-500 for the DVR box and two H24 high def boxes for the other TV's. On the HR24, we are having a problem that if we are watching a show in HD and then go back to a SD channel there is no audio. If you go back to a HD channel, the audio is there but not on the SD channels. I have to do a reset of the receiver which fixes the problem until the next time. We have had the box for three days now and had to do this each day. It doesn't do this on the H24 boxes, jut the HR24. Is it possible the HR24 we got is defective or could it be something else?