Sounds like a bit of hard work for your hardware. In case of poser4 pro, specially when rendering complex scenes some textures just happen to disapear (object is rendered properly, but untextured) They probably are not cached correctly or not cached at all. Let's hope CL will debug their latest project with SR (comming soon). Using poser4, try increasing the amount of virtual memory and free some space on HDD. Hope that helped a bit :)