Many units won't take a digital or 5.1 signal and down-mix that for pro-logic. You will have to have a stereo/2 channel signal for it to produce pro-logic sound. If you are only using 5.1 or digital out from your dvd player, that's the problem. You may need stereo outputs as well.
Should be a pretty nice sounding system once you figure it out.
Should be a pretty nice sounding system once you figure it out.