cycles render result not visible

hi all,
As you can see on the printscreen the 3D smoke effect is “baked” and you can actually see the flames in the rendered viewport, but when i render the animation every frame turns out to be blank, no text no nothing. A print screen with instructions on how to solve this problem would be of a huge help as I’m a beginner to blender.

Please download the blend file here and inspect, and some tips would be greatly apreciated:

thanks in advance! Danny

Look at the render result without a transparent background