[CentOS] kernel panic on 5.6

ok - so I am getting the kernel panic in my (kickstart PXE invironment).
I have used this environment since cents 5.2
The PXE starts up 5.6 gets installed that all works fine.
then after it reboots I get the kernel panic cant mount root (0,0)
This is just one disk SATA nothing special. Same hardware I have always 
used.

I not have booted into rescue mode. my /etc/grub.conf looks fine.
everything else looks fine.

I have tried 3 different machines now. All three get the same result.

I have not changed anything in my kickstart environment from 5.5 to 5.6 
other
than change numbers from 5.5 to 5.6.

What am I looking for? as I mentioned grub looks fine.

Thanks,

Jerry