Hello.
I've compiled today the lastest stable release of the linux kernel (2.6.20), and I've encountered the same problem with the kernel module fglrx 8.33.6-x86. I think it's a compatibility problem. We've to await a new version of fglrx who will correct that :/
Edit:
Somebody have making a patch for the file firegl_public.c :
http://darcs.frugalware.org/repos/fr...x-2.6.20.patch
Download and apply it with the « patch » command (in root: patch < /path/to/fglrx-2.6.20.patch) in the correct directory.