If you’re still running the Beta or RC version of Hyper-V with configured VMs, you’ll want to make sure you do not have the Windows Update feature configured to “Install Updates Automatically”.
Microsoft Knowledge Base Article 950050, the RTM Update for Hyper-V, can be presented for installation by the Windows Update site and due to the servers configuration, be automatically installed. If there are running VMs that were created under the Beta or RC versions of Hyper-V, they could become damaged. The situation can be compounded if those VMs have snapshots and/or saved states. If you are not using a patching solution such as WSUS, you’ll want to be sure to have the server’s Automatic Update component set to either “Download updates but let me choose whether to install them” or “Check for updates but let choose whether to download and install them”
Another way to avoid this potential problem if the Beta or RC1 version of Hyper-V is running is to de-select the option to include recommended updates when visiting Windows Update
We do not suggest this setting, however, as you may miss notifications about other updates that the server needs.
Some examples of the errors you can see when this situation has been encountered are:
“An attempt to initialize the virtual machine saved state failed.”
An error occurred while attempting to chance the state of the virtual machine vmname .
‘ vmname ’ failed to initialize.
Failed to read or update VM configuration.
An error occurred while attempting to change the state of virtual machine vmname .
” VMName ” failed to initialize
An attempt to read or update the virtual machine configuration failed.
” VMName ” failed to read or update the virtual machine configuration: Unspecified error (0x80040005).
If you should run into this problem and then have errors restarting the VMs, this article will walk you through the steps to get back up and running:
949222 Virtual machines that were created on the beta version of the Hyper-V role do not start after the Hyper-V role is updated to a later version
Once KB950050 http://support.microsoft.com/default.aspx?scid=kb;EN-US;950050 is installed, this issue is no longer a concern.
Microsoft Enterprise Platforms Support