I updated a CentOS 5.0 Xen VM to 5.1 (host had been updated already last year) and then rebooted from within. This hung the machine on shutdown with nearly 100% CPU usage. I couldn't shut it down any other way than destroying it. After starting up it would seem to start up, but wasn't available via network or console. Shutting it down would display the same symptoms as before. Finally, I rebooted the host machine and then was able to start the updated guest as well.
This isn't normal, is it? (This was my first number update within a Xen VM.)
Kai