I see this a pretty unique problem considering i havent found anything about it on the forums, creative website and google.
I have a X-Fi Titanium Fatal1ty Pro card with Daniel_Ks 2.0 pack and using DDL so i can send a Dolby Digital 5.1 optical signal to my headset.
My problem is that i can't adjust the volume, kindof, I can adjust the slider etc but it does nothing to the actual volume. I can't mute the master volume. I can adjust individual volumes to, but i'm guessing that's not important.
I'm using a fresh install of windows 7 pro and tried creatives original drivers and now i'm using daniel_ks driver set.
I'm not sure if this is related but i read somewhere that volume can't be adjusted for digital signals.