I'm using a Denon AVR-3805 receiver, an Outlaw 7100 amp, and a Polk Audio LSi series 5.1 surround setup. Up until this evening, whenever I would watch a DVD or play Xbox games, the receiver would default to displaying "Dolby Digital." I paused my Xbox to go upstairs to get something, came back down, and started playing again. Now the receiver simply said "Stereo" and the sound quality was much lower quality than it had been minutes before. I tried messing with pretty much any setting I could find, but I can't get it to go back to Dolby Digital. Oddly enough, my DVD player no longer says Dolby Digital either, instead either DTS Cinema 6 or Dolby ProLogic 2. Same with my HD cable box -- my HD channels used to say Dolby Digital, but now they don't. Anybody have any idea what could've possibly happened here? I made no changes to any settings. I'm using optical cables to connect both the Xbox and DVD player to the receiver. Any advice is greatly appreciated. Thanks.