I know it is totally obvious, but I never tried to figure out how to build the NVIDIA driver for more than one kernel. I always just reinstalled it and assumed it has to be that way. As it turns out I was wrong. With the -k switch you can build the driver for any not-running kernel:
sh NVIDIA-Linux-x86-280.13.run -K -k 2.6.33.4-smp -a
-K builds only the kernel module and does not uninstall the current driver
-a accepts the license
-k is the uname -r output of the kernel to build (you can also use the name of the directory in /lib/modules)