Your composition is good, btw. Lighting in Poser 5 DOES NOT operate in the same way that real world lighting does. The closest comparison -- and one that is somewhat lacking even then -- is Film lighting, or stage lighting. Could you do a combined image made up of screen grabs of the following areas: your lighting ball (the little picture where your light controls are), and the light parameter dials for each of your lights and then the properties for each one. (alternatively, you could save your lightset as an lt2 and make it available). With that information, we could likely help find out what the problem is faster.

thou and I, my friend, can, in the most flunkey world, make, each of us, one non-flunkey, one hero, if we like: that will be two heroes to begin with. (Carlyle)