Data Protector 8 : Error 3 returned from DP VSS API

Data Protector 8.0 error during Exchange 2010 database backup.

Error :  "Error 3 returned from DP VSS API"

FIX :  Include the cell manager and all exchange servers in the "allow_hosts" 

file on each Exchange Server. The file is located at : C:\ProgramData\Omniback\Config\Client