3ds Max: Afterburn problem!! HELP plz

Hello, I'm working on some VFX project and I,ve got stuck due to something in Afterburn that I can't describe

take a look at this animation (200k)


http://yk3d.tripod.com/files/problem.avi


why does it shake? I tryed resseting afterburn and starting on a new particle object using all the default seting, then rendrering, it still jigles! Why so?

Help would be more than welcome....