When you try to connect to a Virtual Machine from the System Center Virtual Machine Manager console you may get the following error (see pic 1). Similarly, In Vista, you receive an error when try to use RDC to connect to another Vista-based PC. Or, on computer running Windows Server 2008 or Vista with SP1 together with Hyper-V RSAT tools, you may receive error when you use VMConnect or RDC to connect to a Hyper-V guest computer (pic 2).
This can occur if you've performed an authoritative restoration on Users container in Active Directory directory service. When this's done the version number of KRBTGT account increases which's a service account used by the Kerberos Key Distribution Center (KDC) service.
To resolve both issues, you can download a hotfix here.