If you have "Remove Back facing polygons" checked, parts of WorldZ doesn't show up in the render, especially the foreground. Nuke the checkmark and it should fix the problem. (One of the first heart attacks I had with P5!) Also, there's a thread about plugging some of the materials into different channels to brighten them up without using lights which works well for sets like WorldZ, (I think it was using the Alternate Diffuse Channel instead of the Diffuse Channel) but I can't find the thread off-hand. I'll look again tomorrow for the thread, if someone doesn't beat me to it by then. Hope that helps!