Please download the blend to try it yourself, with version 2.40RC.
I disovered the following and I think it is a bug :
When I press the “Render button” it even doesn’t render a still image.
I have to press the shortcut, F12 to render it.
When I press the animation button, it doesn’t render…
So, I need to know the shortcut for animation to start proper rendering.
as a workaround… but still it remains a bug if you ask me.
I will post this in the bug tracker if somebody can verify that it is indeed a bug.