Some people have encountered an issue with Virtual Server when they are shutting down the host operating system.  What happens is that they configure Virtual Server to 'save state' their virtual machines when the host operating system is being shutdown, but after they do a shutdown - they find that their virtual machines were not saved, and instead were just turned off (not good).

The issue that is happening is that Windows has a time out on how long a service can take to shutdown before it stops it - and if you have enough virtual machines we can exceed this amount of time - and be forcefully stopped.

If you are seeing this issue (or fear that you might) this KB provides details on how to configure your host operating system to allow more time for Virtual Server to shutdown: http://support.microsoft.com/kb/888745/en-us

Cheers,
Ben