Box2d moves away from sprite?

Hi,

Not sure how to describe this but I have a scene, have added a layer for my game objects. The game layer is much taller than the screen. I have a sprite that moves up the screen when I press a key using a box2d mouse joint. I am using a cc.follow action to keep the layer centered on the sprite. However as I move up the screen the physics object (shown with the debug line) gets out of sync with the sprite on the Y axis. It seems to happen when I get move more than half way up and cc.follow action scrolls the layer.

Here is a pic:

I don’t understand how it’s getting out of line. Maybe box2d does not work with cc.follow? Has anyone else seen this problem. Can anyone help?

Thanks,

Tim