Fairly new with Cycles. I am doing a simple self project. As you can see in the posted images, the preview and the F12 rendering look quite different. The water has displacement modifier which is not being rendered as well as the water material. The displacement modifier is toggled to render. The masonry walls are all UV unwrapped. You can see in the preview the water and the walls render correctly but not in the F12 render.
Using 2.71, win 7 x64. Does this with both CPU and GPU rendering.