Hello,
Antivirus service is running during the backup?
If so, then stop it during the backup.
-- You can also refer the following technote:
What Backup Exec settings can be modified to reduce the amount of time it
takes for a backup to run?]
http://seer.support.veritas.com/docs/249090.htm
NOTE : If we do not receive your reply within two business days, this post would be marked assumed answered and would be moved to answered questions pool.