Help, Invisible Floors

[Havok]

I have no idea whats going on, I made a few maps along time ago and never ran into this problem, its with the house wall textures from weissvulf's website that are not working for me correctly, When i place the walls in the map editor they look fine in the preview picture down at the bottom right, but when I go into the "preview project" some of the texture's aren't showing up like the grass around the wall floors is invisible and only when I get closer to the walls do they show up, So I tinkered around, re-installed and placed the textures in the right folder with no luck still...can anyone help?