Terratec DMX 6fire 24/96 problems?

Hello guys!

I'm having some troubles with mentioned soundcard. The problem is with master volume control. Sometimes when i watch some movies or playing games or whatever, when i try to put down the volume it get's stuck. No master volume can't be controlled anymore. Only the wave play can be. It helps when u reset the machine. But it gets very annoying. Let's say you are listening to some loud music and suddenly you can't put it off.. except via the good old amplifier way, so by the button on the amplifier.

I wrote to terratec support center, but they don't know what is wrong..

I'm using the latest drivers [5.40], latest DirectX, fresh WinXP Pro installation..

Other hardware is:
Asus P4C800E Deluxe
P4 3.0
2x 512 GeiL ram
2x 160gb Maxtor HDD
ATI RadeOn 9800 PRO
Enermax 460w
Plextor 708A
DvD Teac
Logitech itouch cordless keyboard
Logitech MX500 mouse
Logitech Z-560 4.1 speakers


Any idea guys?

Thank you very much!