I have a similar problem - except that I can't play dts encoded movies back. 5.1 audio tracks are fine. The menu option for DTS doesn't allow me to enable it - it is greyed out with no option to turn "on" - all other audio options are enabled - Except that one...
Any help you might provide would be great.
I have an Aussie machine with a DMS3 installed (Version 9). The discs I tried are Aussie and US.