This bug with version 6.5.0 MP5 through 6.5.2a of Veritas Netbackup with the Domino agent has the nice feature of skipping domino NSF's over 2gb and returns a succussful status code "0", telling you the backup for the file was successful, which lulls you into thinking you actually have backups of these files when you do not. The Netbackup logs in fact show "0 bytes" backed up for these, but the reporting mechanisms report only on the status code success. We upgraded a while back, the backup guys were never provided the technote from Veritas (2nd problem), we discovered this by attempting a restore and not having data to restore from.
If you are using this product at those revs and have files larger than 2gb in your domino environment, you may want to look closely at your backups.
There is no current fix for this from Veritas for the 6.1.x and higher revs at this point, a fix is anticipated at some point in Q4 2008 (3rd problem).