Development kernels are not supported by the official Nvidia driver set. From the README:
"All official stable kernel releases from 2.2.12 and up are supported;
"prerelease" versions such as "2.4.3-pre2" are not supported, nor are
development series kernels such as 2.3.x or 2.5.x. The linux kernel
can be downloaded from www.kernel.org
or one of its mirrors."
That said, there are some patches written by members of this forum that will allow you to compile a driver on a 2.5 series kernel. These patches are not supported by Nvidia.