ADT - Windows don't clip walls

I am having an issue in ADT 2006, where when I insert a window, it won't clip the wall in plan unless the window has a 0" sill. I remember that there used to be the ability to change the height at which plan clips occured, but I have forgotten that command etc...

Could someone please tell me how to restore the clip height so it will clip the wall in plan where there are windows?

Thanks!