ok, this is getting really frustrating and (too) time consuming now.
- i deleted the whole landscape and created a new one.
- then i assigned the material to it and the landscape gets covered
with the layer0 colormap:
then i select layer 1, the asphalt texture, to draw it over well, streets and
the surrounding quads change to black.
if i want to paint the layer 0 by hand it turns out black as well.
this is the recent material setup like i sent you via skype: