It's usually down to shadow maps causing this so another way around this with Poser 6 is to render your scene with no shadows and sava as a PNG and then render with only shadows ticked, this will render only the shadows, save this also as a PNG. Take both into Photoshop or equivalent and put them together as layers. Use multiply on the shadow layer and then flatten the image and you are left with a complete image as if you'd rendered it in Poser with shadows on! Save as JPG and that's it, job done!

The beauty of this approach is that you can remove unwanted shadows easily before flattening and even adjust their intensity, colour etc.!

Injustice will be avenged.
Cofiwch Dryweryn.