I built and installed the latest kernel (2.6.28 as of this writing) and attempted to install the proprietary nvidia driver with this kernel. The nvidia installer (version 177.82) did not detect the kernel headers that were in fact installed.

What I had to do was to extract the installation files from the nvidia installer (you do this with the -x flag). Then I had to apply a patch that I found here.

To apply this patch I cd'd into the nvidia installation directory created by running the installer with the -x flag. I downloaded the NVIDIA_kernel-177.82.diff.txt from the link posted above. The patch syntax was:
patch -p0 < /path/to/NVIDIA_kernel-177.82.diff.txt