This just happened to me. I set up a scene with three clothed figures, and when I rendered, the girl's jacket didn't show up. It was visible in preview. I changed the lighting a bit and when I rendered again, the jacket showed up fine. I was very puzzled by it and surprised to see your post on the very same issue.
I am using Poser 8 and rendering in a separate process.
 

Poser 11 Pro, Windows 10

Auxiliary Apps: Blender 2.79, Vue Complete 2016, Genetica 4 Pro, Gliftex 11 Pro, CorelDraw Suite X6, Comic Life 2, Project Dogwaffle Howler 8, Stitch Witch