[vtkusers] vtkImageActor - changing display extent pb

[dean.inglis at camris.ca]

I am developing a simple ortho
slice viewer app that makes use of
1 render window, 1 renderer, 
1 vtkImageActor, i which a radio
button group GUI element should toggle
the views of a 3D MRI data set between
saggital, axial, coronal views.  I only
seem to get the saggital views (data is
512x512x64 slices) regardless of how
I set the display extent.  I have checked
and see that SetDisplayExtent is being
correctly called and acknowledged but 
the renderer simply displays an 'empty'
scene.  Resetting the display extent back
to a saggital view produces the corresponding
correct image.  Are there a few other 
diagnostic checks I could make to figure this
out?  I tried changing from vtkInteractorStyle image
to trackball to see if I was just viewing on edge
but that is not the case: there really is nothing
there.

Dean