Thank you for the hint. It seems the problem lies in the fact that a
"dropFilesEvent" is different from a "dropEvent" and therefore is not
handled by MorphicEventDispatcher>>dispatchDropEvent:with: but by
MorphicEventDispatcher>>dispatchEvent:with: and they handle differently
which morph may get to process the event.
Still i have not yet a solution ;(
http://forum.world.st/file/n4644226/Bildschirmfoto_2012-08-16_um_11.17.35.png