I have a new Onkyo 797 & a Panasonic RP-56 and I had the same problem with a rented Pearl Harbor DVD. I thought that the 797 would take the DTS by auto but you have to make sure in your RP-56 setup menu you have under the DISC tab go to AUDIO and make sure that DTS is set to "ON". Mine was set to off from the factory. I have just watch all of "chapter 11" with the dog fighting over the ocean and the planes crashes into the water and not one skip.....YIPE!!!! Hopefully your problem was as simple as mine (operater error).....