A possible resolution to this issue is the following:
1. Access the NetVault Backup installation directory
2. Access to the NetVault Backup config directory
3. In the NetVault config directory edit the file 'programs.cfg'
4. Add the following at the bottom of the mentioned 'programs.cfg' file:
[Exchange Server APM]
winnt=bin\nvexchangeserver.exe
Make sure the netvault service is stopped whilst doing this.
