I'm gonna go with jroulin on this one ... Aside from your system MAYBE being a little light on horsepower, those settings should be just fine ... one thing I would look at that always sends my machine into a tough render situation, is open reflection maps. See if any surfaces you have in the image have reflections on with no maps, which will force it to render first the item reflected with proper shadowing, and then map that reflection to the surface of the selected item. Just a thought ... hope it helps ...