ASUS Xonar Essence STX. No sund.

Please help me.

I bought this card today. I have put the card in with power from the power supply.
I installed the driver "PCI-STX-090121-8.17.62(Vista3264-RC-01)" from asus homepage.
I have tested two headphones i know works.
I now use Beyerdynamics MMX 300.
The driver program shows that it is taking in sound. Suddenly all music stops and not even my itunes can play the song. I never hear any sound even when it plays. The song freezes or something and I can't see any sound movement in the audio control center. I have diabled the onboard sound card.
I have a GIGABYTE GA-EP45-DS3L/S3L motherboard
OS os windows vista ultimate 32 bit
I have put the headphones jack in the headphone amp
It sais in device manager that device is working.
I have never had a souncard before. it might just be a sully setting. So don't think i pronanly have tried something. I have testes different settings, but nothing happens.
I can't see that i have muted anything in windows, but it really feels that way. But thye freezing of the music in itunes is kinda weard too. Is there a switch on the card? Anything please!