Same problem here and when i tried to install a new kernel show me this:

I did apt-get install kernel-source-2.6.4
ln -s /usr/src/kernel-source.... linux (i tried linux-2.6.1 too)
and when i try to do make menuconfig show that:

root@boxer:/usr/src/kernel-source-2.6.4# make menuconfig
HOSTCC scripts/fixdep
En el fichero incluído de /usr/include/sys/socket.h:35,
de /usr/include/netinet/in.h:24,
de scripts/fixdep.c:107:
/usr/include/bits/socket.h:305:24: asm/socket.h: No existe el fichero o el directorio (file dont exist)
make[1]: *** [scripts/fixdep] Error 1
make: *** [scripts/fixdep] Error 2

Anybody got a "howto" to get nvidia drivers work in knoppix 3.4 whit kernel 2.6.1 or how to upgrade the kernel? Could post a link here please?.
Thnx.