OK, this guy's problem is solved too... but anyway,
Originally posted by zatnktel
the kernel rpm does not install the nvidia.o but the tar ball does
Yes, the kernel RPM does install nvidia.o (assuming you're using 4191). The thing is, though, if the version of your running kernel doesn't match the version kernel that the rpm was built for (which is right in the name of the rpm file, btw), it will install it into the wrong place.
If you download NVIDIA_kernel-xxxx-2.4.18-18.8.0, for example, then it is hardcoded to put the nvidia.o file into /lib/modules/2.4.18-18.8.0/kernel/drivers/video. If you are not running kernel 2.4.18-18.8.0 (if you've upgraded to -24.8.0 for example), then it will appear the nvidia.o never got installed, but it did. It's just not living where modprobe is looking for it.