Windows Vista - External USB DAC - Silverstone EB01

Hello! Just installed Windows Vista Ultimate Edition.

Got one quite large problem.
My external DAC, a Silverstone EB01, does not work that good.

The internal soundcard on the motherboard works OK.... but with the DAC I
get only noise after playing a MP3/Video for a while.
The noise can dissappear after maybe 10-60 seconds. But it will come back
after a few minutes.

I tried updating all drivers I can find... (motherboard, video card drivers
etc). But still no go!
Silverstone does not have any drivers for this DAC, but Windows does
recognize it...

The DAC works excellent in WinXP.

Any suggestions?