NullpointerException

Hy !

I'm working with VisAD now for about 3 weeks and I am really enjoyed about
it. 
I have following problem:

I want to have a VisADSlider on my display. So i construct e.g. a RealType
and a Scalarmap:

RealType x = new RealType("x", null, null);
Scalarmap scm = new Scalarmap(x, Display.SelectValue);

The VisADSlider is constructed the following way:

VisADSlider vslider = new VisADSlider(scm, 0.0f, 1.0f);

Above line throws a NullpointerException. If I print out the stacktrace
for this NullpointerException I get no further information. The
Exceptionmessage is:

java.lang.NullpointerException  
        at myclass.main(Compiled Code)

I wrote a simple program, constructing a RealType, a Scalarmap, the Slider
and a Frame to display the Slider.

??

My working platform is Linux with Kernel 2.0.36 and the latest releases of
jdk1.2 and java3d from www.blackdown.org.
I didn't have any problems with VisAD on Linux. Compilation was no problem
and i wrote some small RMI applications, 3D Visualizations of functions
over regular, irregular grids, ...

Thanks, for every reply, Mike.