You used Booleans to cut out the openings, right? The problem with doing that in Max is it makes mesh that Poser doesn't like, Poser's roundind does weird things with the mix of tiny and big polygons you get. I don't know anything about fixing it in UVMapper, what I do is to try and not use Booleans, or if I do I hand fix the mesh, but welding vertices and cutting polygons untill it is nice and regular. I like nice mesh! Makes it simplier in the long run, too.