I had exactly the same problem. I first tried to install the kernel rpm NVIDIA_kernel-1.0-4191.rh80up_2.4.18_18.8.0.i686.rpm and had all kinds of problems, it said it was installed but startx just produced an error saying it couldn't find the nvidia.o. I tried installing with the source and got the same problem as you. Then I started checking the kernel version numbers using uname -r I found that I was running 2.4.18-14. When I looked under the libs/modules directory I found that I had two directories 2.4.18-18.80 and 2.4.18-14. The first had the nvidia.o installed but n other files, I guest that I must have been trying to install the wrong nvidia driver, so I downloaded NVIDIA_kernel-1.0-4191.rh80up.i686.rpm instead, I tried to install it but it said I all ready had the other installed so I removed the GLX and then the original driver using rpm -e NVIDIA_kernel-1.0-4191.rh80up_2.4.18_18.8.0 etc. and then installed the new drivers using rpm -ivh NVIDIA_kernel-1.0-4191.rh80up.i686.rpm and then the same for the GLX. I then modified my XFree86 file and modules.conf file as per the instructions at http://www.whacked.net/ldl/faq/.
when I typed xstart the NVIDIA flash screen came up!!! an end to considerable frustration. I am a bit of a newbie so I am sorry if this doesn't help, and I still dont understand why we should get that problem with the src file but if it worked for me it might work for you. Good luck.