RedHat Advanced Server comes with a kernel that has changed several key interface functions that the nVidia driver needs. Obviously with these functions changed, the driver won't work!
This is according to this thread:
One workaround would be to install a Linus kernel -- one off www.kernel.org
-- and recompile the nVidia drivers, if that's possible.
Another workaround would be to figure out C (if you haven't already) and patch the nVidia driver to work with your kernel.