NV DVD 2.0 problem with digital sound

Hi,
recently tried the pc connected to a Panny PT-AE100 using
Nvidias NV DVD2.0 and I have to say I was very surprised at
how good the picture quality was and really noticed the
differance when I switched back to my Sony 725.
But I have one major problem....I am unable to get a digital
passthrough to my amp(Sony DB925) for DD/DTS to work.
When I select connected to reciever for ProLogic I get sound no
problem through the SPIDIF but when I change that to connected
to reciever through SPIDIF I get no sound at all????
I know both the coax output on the card works and that the coax
on the amp also works but hust wondering if anyone has any ideas or are they using this software....I found it better than
Powerdvd....no point having a better picture at the expense of
the sound.