Sam,
If you are upgrading to 5.1 only do it on the master.
If its a HPUX server then
Add a new file system to you server, call it /veritas_upgrade and shut off you old veritas, using /sbin/init.d/netbackup stop, make sure all proc's are stopped, run bpps -a. Now copy all data in /usr/openv to the new mounted "/veritas/openv file system. mv /usr/openv to /usr/openv.orig now ln -s /veritas/openv /usr/openv, now upgrade the copy.
Never upgrade the production mount, 4.x to 5.x make tons of changes, so its best to screw up the copy then the production mount. do some testing, if you like it then make it production.
let it sit for a week and do backups if the all looks good then upgrade the clients, for UNIX you can upgrade from the master, if Windows you have to do it from the client, I make the NT guy or Girl take care of that cause it requires a reboot.
here is the link you need
do the java, client and the master.
http://ftp.support.veritas.com/pub/support/products/NetBackup_for_UNIX/
JD