Blank Screen on PDC

When I log on and do CTRL ALT DEL on the PDC NT 4.0 Server the screen hangs and won’t boot up completely. All I get is the background color and the mouse cursor, no icons or taskbar at all. Has anyone encountered this kind of problem. I rebooted the computer several times and now I just left it on with a green background screen with no icons or anything. Problem is I cannot do anything at all. I know still works because it still authenticates users. HELP!