I recently found the explanation to the cropped shadows when rendering in Poser.
It was very simple but I can't remember what I had to do to fix it.

Now I have searched the forums high and low and it has vanished. :(

Help please.

I don't know what you mean by "cropped shadows", but perhaps you need raytracing on instead of the ugly default depth map shadows.

If parts of a shadow that should be there is missing?

Look at your lights carefully. Imagine in your head where the shadows should be.

Then look through your shadowcams. Are you seeing what you should see for each light?
Fine tune the positioning of the shadowcams for each light if they do not match up.

i noticed on a render that part of a shadow was missing,to fix i altered the lights shadow bias to 0.1 instead of the default 0.8 in the material room.hope that helps.

     Another possibility:  Something must catch the shadows;  Look through the shadowcams and see if the shadow would extend beyond the edge of the ground plane.  If so, just scale up the ground plane until it covers all of the area where the shadow will fall.

Thanks everybody! 
It was the shadow cam thingy. All sorted now.

Hugs! 

Glad we could help,
Happy Posering
Tony