I recently ran into a situation where I had converted a Xen virtual machine to a VMware virtual machine. I did so by creating the new virtual machine in VMware and running an rsync from the root of the Xen machine to the new one.
This successfully created the new machine. I then selected the regular kernel to boot into and rebooted the VMware virtual machine. I believe I had to run an selinux restorecon on the / to restore the SElinux permissions but all seemed well after that.
EXCEPT, when I had kernel updates, they would install with a yum install but after a reboot, the system would always boot into the current kernel.
THE CULPRIT: /etc/sysconfig/kernel
In this file the kernel-xen was still listed as the default kernel so the system didn’t know what to update to since kernel-xen was uninstalled so it never correctly updated grub.conf. I changed the default to kernel and viola!