First of all, you should check in your webadmin, if the correct soundcard has been set for your Mediadirector.
I don't know what other steps you have taken so far and what outputs you want to use (analog, digital coax/optical etc) I will go through the steps I did, just to make sure.
Some may frown about it, but the simplest way is to go to the KDE-Desktop of your specific mediadirector.
Open up a terminal and type
This should give you the mixer for your soundcard, where you can check all the available outputs. On most machines the digital output is IEC958. Make sure this is unmuted and the volume is up. This is so far the situation on my core/hybrid. On the ASROCK Ion330, as you read above, the situation was different.
Here the upgrade was needed. If you still have not done so, go now to your ailing MD, open the KDE-Desktop and open up this page again. Download the attached file and open a terminal session.
Move to the directory, where you have saved the file and
tar xvf AlsaUpgrade-1.0.21-4
Wait until its finished...about 15 minutes and then reboot
After that, the sound should work instantly, if not check again with alsamixer.
Let me know how it went.