[CentOS] CentOS 5 sound problems on ICH5

Hi
I have installed CentOS 5 on my computer which has an Intel ICH5 sound 
chip. The card appears as it should, and I can adjust the volume just 
fine. However, when I try to play a sound file(.ogg for instance), 
rhythmbox plays through the file, but no sound is heard. I've tried as 
root, and I've tried doing cat /dev/urandom > /dev/dsp, and it's all quiet.
Output from lspci:
00:1f.5 Multimedia audio controller: Intel Corporation 82801EB/ER 
(ICH5/ICH5R) AC'97 Audio Controller (rev 02)

I've tried a reboot, I've tried restarting the sound system from 
system-config-soundcard, but nothing seems to work. Any suggestions please?
Kind Regards
Jon Jahren