Attached Link: http://www.renderosity.com/viewed.ez?galleryid=911516&Start=1&Artist=randym77

Collision won't work with transmapped hair like Koz's. (Are you trying to use Koz's hair in the Hair Room, or the Cloth Room?)

It does work with dynamic hair, but you have to to do it right. (Link is to an example in the gallery. The comments below the image have links to threads that discuss how to make dynamic hair work in Poser 5.)