Microsoft Hyper-V VSS Writer problem

Configuration Host: Windows Server 2008 R2  SP1 (x64) Guests: Windows Server 2008 R2 SP1 (x64) Problem/Symptoms Windows  Server Backup fails when guests are active: Log Name: Microsoft-Windows-Backup Source: Microsoft-Windows-Backup Date: 5/20/2012 12:40:59 Event ID: 9 Task Category: None Level: Error Keywords: User: SYSTEM Computer: Description: The backup operation that started at ‘‎2012‎-‎05‎-‎20T16:38:15.428000000Z’ has failed because the Volume Shadow Copy […]