Since we rebuilt our servers to windows servers 2008 x64 r2 we have perpetual problems with scheduled backup (shadow copy). In the Application event log, the following events are logged on both nodes: The description for Event ID 4112 from source TsmVssPlugin cannot be found. Either the component that raises this event is not installed on your local computer or the installation is corrupted. You can install or repair the component on the local computer. If the event originated on another computer, the display information had to be saved with the event. The following information was included with the event: VSS processing encountered error 'VSS_E_UNEXPECTED_PROVIDER_ERROR' in the Volume Shadow Copy API 'AddToSnapshotSet'. For more information, see the IBM Tivoli Storage Manager client error log. Re installing TSM didn't change anything and still logging same events. TSM Error log file shows following: ANS1327W The snapshot operation for 'C:' failed with error code: -1. ANS5250E An unexpected error was encountered. TSM function name : BaStartSnapshot TSM function : initializeSnapshotSet() failed, check Microsoft Application event log for VSS errors TSM return code : -1