3D Display Error

Hi, I'm new to VisAD. 

I try to run the tutorial programs in windows NT 4.0 and I have a problem to
execute the 3D graph. (2D is alright). what shall be the problem? Thank you.

Error Message:

Exception in thread "main" java.lang.NullPointerException
        at P3_09.main(P3_09.java:98)

P/S: The OpenGL.DLL file is in proper directory. Do I need DirectX from
Microsoft to generate the 3D graph?

Best regards,