when loading poser, default scene will be those three lites, shadow-mapped, lowest-quality render settings, ground as shadow-catcher.  loading v4 into that should render quickly to produce what looks like poser 4 render.  either you've got a bug or you changed/added something/some setting.  try starting poser, adding some figure other than your v4, and see if it renders black.  with shadow-mapped lites and no ray-tracing, document window may go black while calculating shadow-maps.