Shadows from planes with alpha textur ...

Hi, why do i have the shadow of my whole plane inplace of just the texture from that plane?
I´ve tryed Software/OpenGL rendering - nothing changed.
I´ve also read that somebody solved the same issue while enabling the "force all materials...."checkbox inside the lamps settings. But that does not help i my scene.

What do i have to do?

Im on Fusion7 (free version)

Page 393 in the User Manual covers this, but the surrounding pages give the full shadow workflow, so might be worth a read.

Please send me your manual - mine actual Fusion7_UserManual.pdf has 341 sides an does not explain my problem.