I set up a scene yester day in Poser 5, and did a draft rendering the main window, and all was well. I bumped it up to production, and started it again in a new window at 2025 pixels wide. At the base of the railing object, I got some weird vertical shapes that didn't appear in the earlier version. I re-rendered it in draft mode again int he main window, and it was as it should be. I went back to full size in a window, but this time left the setting on draft, and shapes came back. The left image is the big, production render, and the right one is the small draft mode.