http://www.appleyard.flagonsrealm.com/rogue_trooper_scenario/39frames/nort_acg4_00a.jpg

I have Poser 11. I rendered the image at this link, using Firefly, set in a factory model that I bought in Renderosity. Light from the outside is leaking in between the far wall and the floor, which should not happen. This is a persistent fault in in-shadow parts of Firefly-rendered images. Please how, within Firefly, can I stop this happening?

If I use Superfly, that fault does not happen. But in Superfly I get 2 nuisances:-
(1) The edges of the shadows are too sharp.
(2) Shadowed areas are rendered with a sandy texture.
I have tried various Superfly rendering options, but these faults still happen. Please how can I avoid them?