I've had the very same problem with the very same Linux Distro before
. After hours and hours on the internet after a solution, I realised that would be better to buy a new cheap Linux compatible sound card. I've found a new one from Zoltrix, with 3D Sound support and 4 channel speakers Karaoke for 15-17 US$
(even stands in the box: M$ Win9x/NT, Linux and DOS, which is hard to see nowadays Linux when you buy something...). It was a great investiment. I just don't fight Linux hardware support anymore. I'm 23 years old and half of my hair is grey thanks to Linux
lol.
Well, if buying a new sound card is not your option, hope someone else will help you.
Good luck.