That might have something to do with the RENDER extension that nVidia replaced in 4191. Maybe -- I'm not sure though. I don't know what's all involved in playing DVDs.
You can install 3123 over top of 4191 with the tar files easily, and since you would be installing from tar files, it would work with every kernel, as long as the source for that kernel is installed and configured. If you get errors trying to make, post them; they're probably happening because of kernel-source.
Actually, .src.rpm's would probably work as well, but you'll have to remove 4191 first: rpm -e NVIDIA_GLX ; rpm -e NVIDIA_kernel