Just ran across your post, a bit late but I will reply anyway...
I had a similar problem when I upgraded from Fedora 3 to 4, though the problem I had also affected video. What I found was that there are some issues with the Intel on board 8x0 chipset (mine is the 810). Intel has not been updating the drivers for this particular chipset and one of the shared libraries is no longer compatible with the outdated driver. There are some hacked drivers out on the net but I was able to resolve the video and sound issues by running a yum update on my system. I never did find out exactly which libraries were causing the problems though but obviously the update did the trick. My recommendation would be that you make sure all your libraries are up to date and go from there.
I do find it rather odd that Intel isn't keeping up with the chipset drivers as this chipset is used in the Dell Power Edge SC430 servers...Ill send an email to program management at Intel I am sure they will get right on it