Ok, i've found out, that it does not work with the provided library.
But it works, if i define blocks myself.
So i have to insert the library block, then explode it and then modify it and then save in another file...
And then inserting a block works.
But if i modify the block, it looses the ability to retain the attributes of the layer. This happens qeual if i move, rotate or scale the block.
This definetly is not working....