Hi all,
It may be my setup but this is what I found.
Current yum update.
Only breaks xen boots.
Most recent yum upgrade to 3.8.1-201 omits the initramfs line in its
grub2.cfg file.
After adding these lines it boots.
echo 'Loading initial ramdisk ...'
module /initramfs-3.8.1-201.fc18.x86_64.img