Wish I could offer some assistance, but I'm experiencing the same thing. I'm running RH 8.0, and I just built a 2.4.21 kernel with the low-latency and preemptible kernel patches. After some initial problems with my grub configuration, I was able to boot into the new kernel. Unfortunately, all of the modules fail to load. I followed the instructions here:
I received no error messages during the process, but the new kernel won't load any modules.
This isn't the end of my problems either - my X configuration is broken when booting my old kernel now.
I suspect a connection between these problems, but I'm not sure what it is. Can you still run X under your old kernel?
"The trouble with computers, of course, is that they're very sophisticated idiots."