Garbage matting

Hi,
I tried to do the tutorial about the Garbage Matte for Blender 2.48 in the book Mastering Blender.
I made it myself.I don’t know if I’m right but until page 134 all seems to go according to the pictures.
At this page however I don’t have the result shown on the picture and I don’t understand why.
In the book the garbage matte hidesthe background, not on my .blend file.
I’ve done everything … my beginner mind can think of :-).



What did I miss ?