I am having the same DirecTV issue on my HR22. Audio and Images work without issue, but I can not get sound playing Video. I just tried MC 17.0.99 running on a Win 7 x64 machine (brand new build w/ i7/8GB RAM). Advanced settings are set with only DLNA checked. I have tried all the MPEG2 settings.
MPEG2 and MPEG2 PAL low/med/high do not work. Certain .avi container titles show up with an x (unplayable). The titles that show the camera go to please wait, black screen, then auto close back to the previous channel. One note, less files show up with the x using the PAL option.
MPEG2/DVD Stream: Again, certain .avi containers and .wmv show up with the x (unplayable). Most playable titles give the error message "the audio was unplayable, play video without audio" with yes or no options. Some (certain .avi containers) just play the video without audio with no error message.
MPEG2/DVD PAL Stream: Oddly enough, this gives me the "best" results. All titles show up with the camera (playable). However, I still either get a no playable audio error message or the video just plays without audio.
I have not dove into which .avi containers are using what codecs, audio tracks, etc since none work--just sort of been scanning through my library trying to get something to play. Also, I should note that these files play fine in the MC on the PC.
It appears that this is an issue that has been broken since MC15:
http://yabb.jriver.com/interact/index.php?topic=62603.0