View map in viewport

I just started working with Viz 2007, until now I worked with 3d Studio Viz 3.

I've imported an AutoCAD 2007 drawing. When I first apply a standard material
like grass, I can see the mapping in the viewport. But when I create my own
materials, like masonry, I can't see the mapping....
When I first create my own material, and then want to apply a material like
grass, I can't see the grass mapping as well....

It's probably the small "show map in viewport" button that is not
enabled. the button is a blue and white cube below the sample spheres to the
right of centre.

Nope, I've tried that button.

What I don't understand is that when I start a new file, the mapping will show
when I use a material from the library. But as soon as I create my own