Backupexec 2012 CAS Server - Credentials Fail

HI All,

I have the following setup:

2 x Managed Servers (BackupExec 2012) (Fully patched)

1 x CAS Server (BackupExec 2012)(Fully patched)

I have other physical and virtual servers backing up (registered through the CAS) with no problems, however when I try to add a job for the CAS server itself the credentials Test Stall's.......forever......and I can not proceed with the backup, Every other machine I add works fine and I am using the same credentials for all servers.

Are there any special requirements for backing up a CAS server??

thanks

Bernie.