NW6.0-SP5 with BE91, last Build

When running our daily Backup-To-Disk-Job (including a full
verify) this job sometimes ends with an error.

The job-log does not show anything special, only at the end
comes the hint below:

##NML##=========================================== ==========
===================
##NML##JOB SUMMARY INFORMATION
##NML##-----------------------------------------------------
-------------------
##NML## Job name: DISK DAY
##NML##Job run number: 461
##NML## Job type: BACKUP
##NML## Submitted: 03/24/06 at 04:30:50p
##NML## Policy name: DISK DAY
##NML## Backup method: Full
##ERR## Job completed: With ERROR - Media format
inconsistency has been detect-
##ERR##ed. (24616)
##NML##-----------------------------------------------------
-------------------
##NML##Job was rescheduled after completion.
##NML##Rescheduled for: 08/29/07 at 08:00:00p
##NML##Job was scheduled to run every 1 Day(s).
##NML##=========================================== ==========
===================

Since we are talking about a b2d-job here with disks as
source and target (Seagate SCSI320-something-disks with
Adaptec 29160-controller) this message always causes a
little headache. The Symantec-Knowledge-Base does not give
much help. Has anybody here seen this before and any idea on
how to get rid of those errors?

Sincerely

Karl