My smoke domain model is rendering

Hello.
I’m using Blender 2.61, and am attempting to use a smoke simulation in my scene. Everything is working great in the viewport, but when I try to render it, my domain is rendering as a solid model, which blocks the view of the smoke.

The domain has no material applied to it.

How can I make my domain render invisible?

Thanks.

P.S. How do I change the color of my smoke?

Take a look at this Smoke Tutorial.

is it possible to freeze one one frame of the smoke sim? this were cool, becouse you can rotate the camare around a smoke cloud or an explosion. or is this possible on a different way?