7VAXP Ultra digital output question

Hi all

Got a quick question about outputting through the spdif socket into my 5.1
amp. I've got it all hooked up, but I can't get any sound from the rear
speakers unless I'm playing a dedicated 5.1 source through say Power DVD.
Also I can't get any sound when I use my TV card (Hauppauge WinTV Go), but
I've also hooked up an auxiliary source (albeit in stereo) to compensate for
this.

I've got the latest drivers installed, when going through the soundman
program, I can test the speakers, but only left/right work. If I use the
HRTF Demo to check sound, I get left/right/centre but no rear and no
subwoofer... in fact when it's supposed to swing around to the rear
speakers, it plays through the front ones.

Spdif-Out is set to both digital and analogue, changing this has no effect
apart from setting it to no output or throughput.

Yes it. set to 6 speaker (5.1), yes everything is hooked up correctly... but
there must be something I'm missing because if I play a DVD, I get great
sound apart from a pop/crackle when it's switching from one title to
another.

Any help appreciated
Thanks
H