I was not able to run your applet so I have to guess what the error
could be. Nevertheless I guess it is a problem with some static
parameter. I realized that IE and maybe Netscape do not reinitialize
static parameters when you return to a page that is allready in their
cache. Because of that I often got Exceptions like NullPointer or
ArrayOutOfBounds. You should check the Java console for exceptions.
By the way I saw no static parameters in your program. Perhaps the
problem lies somewhere in VisAD or Java3D.