To sum up, You must run a digital cable, either optical or co-ax from the dvd player to the receiver unless the player has a dts decoder (usually found only on dvd-audio capable players). If the player has a dts decoder you can use the 5.1 analog cables to the receiver and put the receiver in analog direct mode. In this mode the receiver will not display dts, as it's dts decoder is not being used.
In order to get your receiver to decode dts from the digital cable, you must enable dts output in the player's setup menu. Players are almost always shipped with dts digital output disabled the dts signal can cause damage to speakers if no dts decoder is used.
You also must select the dts track in the dvd's setup menu.
I have a 6.1 reciever and when i switch the dvd to 6.1 i get no sound. I do have an optical connection from dvd to reciever. I tplays in DTS-ES. Is that good? The rear center channel does work in this mode.
I just tackled a similar problem last night when I tried to watch Gladiator in DTS-ES mode.
My DVD player has an optical cable connection to my receiver, so I was getting Dolby Digital just fine. But when I tried to play the DTS track, I got no audio.
The problem was my DVD player was outputing DTS in PCM. So all I had to do was go into the DVD player's setup menu, and change the DTS output to BITSTREAM. Voila, beautiful DTS-ES sound to my receiver.