I just finished trying to compile the 2.4.22 sources from kernel.org, with no success. I got them to install, but had a horrid time running them. I obviously didn't configure it correctly; and even then, the AGPGART stuff didn't start correctly. I got the same error messages. I rolled back to the 2.4.20-18.9 kernel I already had running.
I am using the stock RedHat kernels. I realize this probably contributed to my less-than-successful attempt to get 2.4.22 running.
I've read that the nVidia patch does not work right for the RedHat kernel sources, is this true? I had tried at one point, but couldn't get it to work correctly. Perhaps I'll try again.
Interestingly enough, if I look at /proc/sys/nvidia/agp/status (i don't have the exact path handy...), it says AGP is running. If this is so, what exactly does AGPGART do?