I recently encountered a customer issue where, periodically, for what appears to be no reason at all, while a user is working in a Virtual PC (virtual machine in Windows Virtual PC for Windows 7) - it will hibernate on its own. In some cases, the user was in the process of doing work.
At first I did not think that would be possible but it was quickly confirmed. A quick investigation confirmed that MED-V 2.0 was installed - yet the user was working outside of MED-v using the Virtual PC in VPC only - or full desktop mode.
We also noticed the following event was being logged in the MED-V event log at the same time this was occuring.
Event ID: 11004
Task Category: Guest Patching
Message: "VM is being stopped during the configured update window."
It turns out the Virtual PC was interrupted by the Guest Patching Service of MED-V 2.0. What we did to resolve this was adjust the registry value GuestUpdateDuration in the registry key (HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Medv\v2\VM) to 0. This prevented the problem from re-occuring.
MED-V assumes it will be waking a VM up when not in use by MED-V. When the same VM used by MED-V is currently opened exclusively by VPC in full desktop mode, MED-V tiggers VPC to close the VPC using its default action (hibernate.) The value GuestUpdateDuration defines the number of minutes that MED-V should keep the MED-V workspace awake for updating, starting at the time contained in GuestUpdateTime. Enter 0 to disable.
Remember that MED-V v2.0 was only designed for provisioning applications to run in seamless mode.