Which Poser version are you using?  

Another post similar to this issue was solved by removing Ambient Occlusion from the lights.  I would suspect that if you are using a current Poser version, the AO nodes might be causing the problem.  However, we have no further information about light settings and render settings.  The material shader arrangement for this character is overkill IMO; simplification would be a better option for current Poser.