No sound through SPDIF

Hi! Recently I bought a DVD software decoder: Power DVD and I'm trying
to watch a movie on it. But the problem is I can't hear any digital
sound and my speaker system (DTT 2500 Digital) doesn't seem to sence
the DD format (no light appears when watching the movie). This is
happening when I choose the SPDIF sound output in Power DVD's
settings. When I choose 4 or 2 spekers I hear the sound correctly.
Here is my configuration: my Pioneer DVD player is connected to the
IDE connector and also the digital output 2-pin cable is connected to
the SPDIF input of my SBLive! Platinum card. The SB's Digital Out jack
is connected to the DD (AC-3) SPDIF input of the speaker system. Also
the SB card is connected to the LiveDRIVE II which in turn is
connected to a Digital DIN ad-on fitting in the PCI slot to which the
Digital DIN cable is connected which fits the Digital DIN input in the
speaker system. I understand that the SPDIF signal is processed not
through the digital DIN but through the Digital Out jack but unpluging
the DIN cable doesn't change much. Please help me cause I can't seem
to find a sollution to the problem. Waithing for your reply!
Greetings!