Cause - Windows guests did not acknowledge an "xm shutdown -H" operation started from the host.
Consequence - Attempting to turn a Windows virtual machine off with "xm shutdown -H" will not have any effect. Furthermore, it will prevent "xm shutdown" from working until the virtual machine is rebooted.
Fix - The paravirtualized Xen network driver trigger a shutdown of the virtual machine when "xm shutdown -H" is sent.
Result - (same as fix?...)