Win NT 4.0, unlocking screen saver

Win NT 4.0 SP6a, network enviroment, logged in to NT 4.0 Servers.
I have a user who occasionally has a problem with the screen saver unlock. When she tries to unlock the screen she does not have the DOMAIN line and the system will not unlock. Administrator accounts cannot unlock system either. She has to reset the system. She is using the 3d pipes that came with NT.