NoClassDefFoundError

when I try to run RubberBandBoxRendererJ3D I get the following:
      Exception in thread "main" java.lang.NoClassDefFoundError:
javax/media/j3d/Group
also when I try to run TestArea in data/mcidas I get the following error
      Exception in thread "main" java.lang.NoClassDefFoundError:
com/sun/j3d/utils/applet/MainFrame
I was actually able to run TestArea a few days ago, but I'm not sure why
it won't run now.  Also when I ran this routine with a larger size file
(a 14mb 4 km conus area image) I get the following error
      Exception in thread "main" java.lang.OutOfMemoryError
Can you shed some light on these NoClassDefFoundError problems and how
can I overcome the memory problem.  Thank you.

-Ken