By now I'm not even faintly surprised at what this program does. I have a texture selected in the color texture node, it's connected to the diffuse and highlight sockets and it shows up nicely in the preview window, wth Jessi on the flat roof looking at the sunset. Do any render and J and the house are there, with lovely long shadows, but the ground has vanished. 

I'd show you the screen shots but this thread won't allow any insertion of images. It deleted my text when I clicked on the icon last try.

The manual ,as usual, is deafeningly silent on this topic : anyone know what the (probably simple but wonderfully well hidden) answer is??