in this TID : http://www.symantec.com/business/support/index?page=content&id=TECH214822
you can read :
The Backup Exec Media Server Operating System should be at least the same version as the Operating System of the VM being backed up via GRT to avoid this alert being created.
in another TID, if you want to do a backup GRT of an AD on a windows server 2012, you need to have a media server on a windows server 2012.
veritas support recommand me to upgrade the OS of the media server to Win server 2012r2
it doesn't solve all bugs
we can't do a GRT backup of an AD using a grt backup of the VM, we must to do a backup of the server using the windows agent
we have lot of errors on diff backups of a sharepoint 2010 on a real server.