BACKUP EXEC 2010 Exchange 2007 snapshot does not have valid data

V-79-57344-34070 - AOFO: Initialization failure on: "Microsoft Information Store". Advanced Open File Option used: Microsoft Volume Shadow Copy Service (VSS).
Snapshot provider error (0xE0008516): Resources specified for snapshot do not have any valid data on them. Check if files were deleted or renamed.
Check the Windows Event Viewer for details.
V-79-57344-34070 - AOFO: Initialization failure on: "Microsoft Information Store". Advanced Open File Option used: Microsoft Volume Shadow Copy Service (VSS).
Snapshot provider error (0xE0008516): Resources specified for snapshot do not have any valid data on them. Check if files were deleted or renamed.
Check the Windows Event Viewer for details.

VSS writers show no problems.

have tried reinstalling the remote agent on the exchange server, but still get same error.

windows 2008 server, running exchange 2007.