Fedora Core 6 has recently been updated to Kernel version 2.6.22.5-49. When you depend on compiled kernel modules, as in the case of nVidia drivers from Livna, you have to update them too. Livna does a nice job of providing updated drivers as soon as, or even earlier, Fedora repositories are updated. However with the recent release of Fedora Core 6, the Livna repository is presenting the kmod-nvidia driver version 100.14.19-1.2.6.22.7_57, which works only for Linux kernel version 2.6.22.7-57. So you are forced to either use the old kernel version 2.6.22.5-49 and wait for a compatible update from Livna or forgo using nVidia drivers, which is most likely an unacceptable solution. Fortunately the solution is simple. Here are the steps

1. Download the appropriate kmod-nvidia rpm from livna repository: kmod-nvidia-100.14.11-1.2.6.22.5_49.fc6.i686.rpm

2. Update / freshen your nVidia drivers with the following command and reboot:
rpm -Fv kmod-nvidia-100.14.11-1.2.6.22.5_49.fc6.i686.rpm

That is all you need.

Note: Do not update this or xorg-x11-drv-nvidia rpm from Livna at this time.

I am not sure why Livna isn't presenting the proper rpm. My guess is that their repository meta-data is incorrect.