Windows 2008 R2 Hyper-V hotfix

You cannot run a Windows 8-based or Windows Server 2012-based virtual machine in Windows Server 2008 R2 Hyper-V

http://support.microsoft.com/kb/2744129

You create a virtual machine that is running Windows 8 or Windows Server 2012 on the computer. However, you experience one or more of the following issues: 

• The virtual machine stops responding.
• You receive a Stop error message, and the computer restarts. This behavior stops all running virtual machines together with the computer.