X won't start after update to latest kernel

[Claude Jones]

I see several problems being reported with the latest 2.6.18-1.2200 
kernel. I just updated the kernel and kernel module for the ATI card 
from the Livna repo. My system is now completely unable to start X. I 
tried booting to runlevel three, but no dice. Tried booting into the 
three previous kernels I still have on my system, but X won't start with 
those either. This seems a little different than other problems being 
reported. Any one have a thought? It seems strange that all the kernels 
have this issue - someone else reported they were able to boot in the 
previous kernel.