If I'm not mistaken, to install the src you should use rpm -ivh kernel_version.src.rpm . It appears that rpm is confused with the --rebuilddb option and then an rpm.
IMO, using the tar.gz file and a manual install for nvnet is solid and works whether there is a compiled version for a kernel or not. None of the other bagage in the nforce package is used and is a short and sweet install.
Make sure the kernel source is installed as per the above discussion.
Then get the NVIDIA_nforce-1.0-0261.tar.gz file.
Extract the source
> tar xvzf NVIDIA_nforce-1.0-0261.tar.gz.
> cd nforce/nvnet
> make clean
> make install
Check that your /etc/modules.conf file has the following entry: alias eth0 nvnet
Check that the module is in the right place by:
> ls /lib/modules/`uname -r`/kernel/drivers/net/nvnet.o
> insmod nvnet
> lsmod | grep nvnet (to see that module is loaded)
> ifup eth0
> ifconfig -a (check that the network came up)
And if all went well - enjoy.
Then reboot and check that the module gets loaded on boot (lsmod).
Maybe this will be of value ......