Tile Map tutorial

I'm trying to implement the tile map tutorial that come with the free trial version but I have the following problem:

when I'm trying to to implement the brushes (in page 6) I need to select multi brushes like this: "hold down Alt while dragging across a set of tiles"

but it does not do it? when I hold Alt and drag the mouse the blue box will not select anything (or the multi selection will not happen)

why this happen? and does it happen with anyone else?

thanks in advance.