Backup Exec 2014 System State Access Denied

Hi,

I'm running Backup Exec 2014 on a Windows Server 2012 and a job that is backing up a Windows Sever 2008 System State is failing with the below messages I've included below.

The system being backed up also runs Exchnage and is a DC - I know, terrible, I need to change that.

The system's exchange and data settings all back up successfully

All other systems and DC's back up successfully.

The Test credentials is successful. I have tested and run the backup with the domain admin account and the <use server's logon..> account for the system as a whole as I can't chnage just the System State Logon Account. All other backup jobs use the 

Job ended: Wednesday, 29 October 2014 at 3:12:52 PM
Completed status: Failed
Final error: 0xe0008488 - Access is denied.
Final error category: Security Errors

Backup- \\serv.child.domain.com.au\System?StateV-79-57344-33928 - Access Denied. Cannot backup directory \ and its subdirectories.