I have never had good luck getting my .mkv files to play using DD or DTS. I usually have to sacrifice a sheep, make sure all the planets are aligned with the Earth, pray to the DTS and DD gods before I even attempt to get things working. Then, after hours of frustration, I will do something unreproducible to get it to work. Then I make everyone tiptoe around the rumpus room, whispering love mantra's to all things JRiver. This scenario has replayed itself many times over the years. This is why I hate updating MC. Usually the updates don't bother my settings, but occasionally they do. Then it's off to Costco to buy another sheep.
To be fair, my HTPC is 3+ years old, running XP. I have so much time invested that as much as I want to install Windows 7, I can't quite muster up the courage to do so. I have 2 HDPVR's and 2 PVR250's running BTV so smoothly, it's like an appliance.
I was so tempted to update to the newer builds with RO, but I resisted as Costco was out of live sheep the last time we went. Boy, am I glad I resisted. In theory, RO is exactly what I want, but I will wait until all the bugs are out and I am good and drunk before I give it a shot.