Stuck on preparing scene data

Hi Everyone,

I am new to blenderartist and I have a problem.
I’m trying to render an animation in blender (internal render) which I have done a few times.
But now when I render my animation blender gets stuck on preparing scene data, it only happens with a few frames not every frame.
I’m currently using blender 2.72 and I have already tried a previous version without any succes.

Does anybody have any experience with this problem or knows how to solve ?

Kind Regards
Bryan