Problem with 2d display rendering on Mac

I have installed visad on a G3 Macintosh powerbook, running Mac OS X
public beta.  I have a routine similiar to Test39 that displays some
data using the 2D display, but runs as an applet.   When I run the
routine using appletviewer the window pops up, the color widget shows up
at the top and the white outline around the image shows up along with
the axes (and the axes labels).  However, the Image itself does not show
up and the following error is printed out in the terminal:

          java.lang.ClassCastException:
java.awt.image.MacGWorldDataBuffer
            at
visad.ShadowFunctionOrSetType.createImage(ShadowFunctionOrSetType.java:2962)
            at
visad.ShadowFunctionOrSetType.doTransform(ShadowFunctionOrSetType.java:2100)
            at
visad.java2d.ShadowFunctionOrSetTypeJ2D.doTransform(ShadowFunctionOrSetTypeJ2D.java:99)
            at
visad.java2d.DefaultRendererJ2D.doTransform(DefaultRendererJ2D.java:101)
            at visad.java2d.RendererJ2D.doAction(RendererJ2D.java:136)
            at visad.DisplayImpl.doAction(DisplayImpl.java:1006)
            at
visad.java2d.DisplayImplJ2D.doAction(DisplayImplJ2D.java:308)
            at visad.ActionImpl.run(ActionImpl.java:225)
            at
visad.util.ThreadPool$ThreadMinnow.run(ThreadPool.java:86)

Could you possibly shed some light on why this error ir occurring and
how I might fix it.  (P.S.  this routine works fine on a linux-based
PC).   Thank you


-Ken