[CentOS] Has anyone had success getting on-board sound to work on a Tyan S2895?

My setup is as follows:

Motherboard: Tyan S2895
CPU: Two Opteron 275s
Memory: 4 GB
Disk: Three 250 GB SATA drives attached to a 3Ware 9500S-4LP RAID card
Video: Nvidia GeForce 7800

The only hardware that I have added to the motherboard is the 3Ware card
and the Nvidia card. The disks are configured as a RAID 5 array, and the
machine boots from this array. I installed CentOS 4.2 x86 on this system
without any problems during the installation. The on-board sound card
was recognised and the correct driver (snd_intel8x0) installed to handle
it. However, on rebooting into the SMP kernel after the install, the
installation proved to be completely unstable. The kernel would panic
sometimes during startup and sometimes during shutdown. The uniprocessor
kernel seemed to be stable, but I noticed the following error messages
appearing on the console during startup (the same error messages also
appeared when booting into the SMP kernel):

3w-9xxx: scsi0: ERROR: (0x03:0x0104): SGL entry has illegal length:address=0x37077000, length=0xFF, cmd=X.

Suspecting that there might be a driver incompatibility with my
particular hardware configuration, I downloaded one of the Fedora 4
kernel sources from the 2.6.12 series, and compiled my own SMP kernel.
This solved the stability issue, and I have been using this intensively
for four months without experiencing any system crashes. Unfortunately,
I have been unable to get the on-board sound to work. If I use XMMS to
play an MP3 file (I have the XMMS MP3 plugin from the Dag Wieers
repository installed), then on hitting the play button nothing happens.
It is not that XMMS thinks that it is processing the file but no sound
is being produced, rather the playback counter stays at "00:00". If I
visit a web page containing a Flash animation with sound, Firefox locks
up and has to be killed. I have compiled other Fedora kernels from
source (2.6.14) and the same behaviour is observed. I also cannot get
sound to work with the 2.6.9 uniprocessor kernel supplied with CentOS
4.2.

I know that the hardware on the motherboard is not faulty, because the
machine is set up to dual-boot into CentOS or Windows XP. On Windows,
there is no problem with the sound, and interestingly once I have booted
into Windows if I then reboot into Linux then the sound will work under
Linux (although sound mixing is still a problem - one application
outputting sound will cause a second application trying to output sound
to stall until the first is finished).

Has anyone on this list experienced the same problems, and if so found a
way to overcome them? Failing that, does anyone have any suggestions for
any tweaks I can make to my system to make the sound work without having
to boot into Windows first?

Thanks,
David Mellor.