the top render looks o.k. to me for a poser 4 render.  maybe touch it up in PSP if it's critical
to have it look right, or use carrara or some real renderer.

obviously there were many problems with poser 4 rendering engine and the way it calculated
backlites, shadowmaps et al.  e.g. poser 4 calculated the additive shadow wrong in cases
like this, where there were opposing back and front lites.  there is a recent post in this forum
about said bug.  adjusting the backlite shadowmap size and zooming in on the backlite
shadowcam wouldn't work in this case AFAIK.  and that's why folks used spots in poser 4 -
so they could avoid zooming in on the shadowcam (little-known feature of poser 4).