I have experienced this in the past, and Symantec Support rightly called it a license issue.
You can back up to tape but not to disk. Is this a tape based license issue on the proxy server.?
Some technotes and previous forum posts on VCB and licensing:
GENERAL ERROR: VMWare Consolidated Backups (VCB) are failing with "system error occurred(130)"
http://seer.entsupport.symantec.com/docs/298951.htm
NetBackup 6.5 VMware Consolidated Backup Agent License key requirements
http://seer.entsupport.symantec.com/docs/319255.htm
https://www-secure.symantec.com/connect/forums/netbackup-vmware-licensing-requirements