Why, Render move object out from sight

< http://vimeo.com/2263639 >

I need your advice. I have animated a fellow, sitting in a room, with three walls.

Why, the backwall (Red ) disaphere together with the fellow in the beginning of render and why the render moving the objekt away. I have not chang the camera position.

Do you have any ideas.

I try to attach a Blender file ,to big 1.2 MB Sorry

Thanks in advance.