rpm -qa | grep GLX
prints nothing? If it prints nothing, then you don't have an older version of the NVIDIA_GLX package installed. Many distros (Mandrake, for example) don't. I know SuSE does, but I don't know about RH.
If you don't have an older package installed, then go ahead and install the version you have again.
Are you sure you made the necessary changes to /etc/X11/XF86Config (or XF86Config-4 if it exists)? This is detailed in the README, so I would think you did. But you say nothing about it, so I figure it's probably a good idea to ask.
If it still doesn't work after installing NVIDIA_GLX and editing your X config file, then attach your /var/log/XFree86.0.log file. It will probably have some indications of what to do in it.