So for clarity you installed 6.5GA - this was working OK - then after a period of time you installed the 6.5.4 update for that OS/platform and this is a master server you installed it on?
You could rollback to the previous version. On UNIX/Linux /usr/openv/pack/ holds the previous backed up binaries prior to the update, with a uninstall scripts. However, I would advise this would be a last resort.
I would review the install trace log for the update and see if it had any issues with it.
For UNIX/Linux it normally places them in /usr/openv/tmp
Windows should have something similar under the <install_path>/Veritas/NetBackup folders
The community might be able to assist further with some more information on your environment.