Reality Factory

I've searched the forums but I haven't found any help, so what happens is when I try to resize a box I get this error saying "Brush = = Null" and If I click ok or exit out, it shuts down reality factory, anyone know of any suggestions?

That usually happens if you are using a hollow brush and the wall thickness is set too thin. Make sure the wall thickness is reater than2 or 3 texels and that the brush is not too small if it is hollow.

ok trying now

ok well I'm trying to create a door, and doing exactly what it says in the faq, but it keeps on doing it