The Echostar VIP 722 receiver is a very nice DVR. It can play and record TV from both over-the-air DTV broadcasts, and from satellite. It has one OTA tuner and two satellite tuners.
One of my most frequently watched channels is PBS, specifically KQED out of San Francisco. The 9.1 subchannel is their HDTV channel.
I have found that on half the broadcasts, the Echostar 722 displays a picture on 9.1, but is unable to decode the sound.
In the process of setting up a software DVR on my HTPC, I found that it can decode the same broadcasts, with sound. This is a problem with the 722 DVR.
I filed a report to Dish network tech support and had the issue escalated to their engineering department. I will update this page if I get a response.