Microsoft also released a hotfix for Hyper-V where you cannot connect to a virtual machine by using the Hyper-V Manager MMC snap-in in Windows Server 2008 R2. The situation is:
“When you try to connect to a Hyper-V virtual machine by using the Hyper-V Manager Microsoft Management Console (MMC) snap-in on a computer that is running Windows Server 2008 R2, you cannot connect to the virtual machine. Additionally, you receive the following error message:
Cannot connect to the virtual machine. Please retry.
Note This issue does not occur when you connect to the Hyper-V virtual machine by using Remote Desktop Services.
This issue is caused by a function failure that occurs when the connection uses the VMconnect.exe command line”.
A supported hotfix is available from Microsoft.