I want to add motion blur to this scene:

This scene consists of the the two following images:


So when I add motion blur to the first image, I get this result:

When I turn on the environment layer, I get this horrible result:

I can’t really figure out what’s happening here. What causes the dark halos? Tried blending modes in Photoshop and stuff, nothing seem to help. How can I make this looking right and realistic?
I’m using After Effects CS5 and Photoshop CS5.