I too was getting this error message. It appears to be related to selecting (within a backup job) the following Backup Exec entities on the media server:
"Microsoft SQL Server "BKUPEXEC"
"Microsoft SQL Server "MS_ADMT"
I was told these entities represent the job catologs that are maintened by Backup Exec. And because these objects are automatically backed up internally at 4:00AM every morning into a flat file underneath the "c:\program files\symantec\backup exec\catalogs" directory, that these two entities do not need to be selected in your backup job selection list.
Since the "\backup exec\catalogs" directory is part of the C: drive, the catalogs will be backed up (to tape or B2F) when the backup job naturally progresses the folders of the "C" drive (assuming the C: drive is selected for backup).
Once I deselected these two entities, the error messages went away.
However, this does not explain why the system bombs on these objects, even in cases where one has also purchased Backup Exec SQL Agent.