|VSS = Volume Snapshot Service or Volume Shadow Copy. |
It is a function built into Windows to allow Backup applications to backup files that are open and in use, something that prior to Windows XP was not possible.
The error would indicate that the backup has completed but has probably missed files that were open because VSS is not working correctly.
Look in Services under column shadow Copy to see if service is running. If not, enable it.
Check the event viewer to see if there is anything in there.
message edited by StuartS