I've tested a couple of DTS-HD 3.0 discs, and in all versions of the Arcsoft decoder, I can confirm that they're being decoded to a 6 channel output; but I am getting audio in L/R/C with LFE/SL/SR being silent.
If I mute the center channel via the Parametric EQ, I'm only hearing music/ambient noise, and if I mute the L/R channels I only get dialog. (just how those films were mixed I suppose)
It may just be that disc?