Change of admin pw breaks veritas backup

I am currently running Veritas Backup Exec 8.6 on a windows 2000 server. After changing the admin password. Veritas gives errors saying that it can’t start the naming system due to login error. When I click on the app to open, it brings up a logon screen asking for admin password and neither old nor the new passwords work. I have had to change the password back to the old one and reboot server (not just log off and back on) to get the backup program working again. Any ideas are appreciated.