[System.sun.java2d.opengl=true]

In the Brettspielwelt.prop you must write
System.sun.java2d.opengl=true

-D is for the commandline But thanks for the hint.

Err..indeed. Thanks also

[System.sun.java2d.noddraw=true]

write this line in your Brettspielwelt.prop
System.sun.java2d.noddraw=true

Or even better try do write instead this one:
-Dsun.java2d.opengl=true

The client becomes so many faster this way, its unbelievable

Overview about java2d properties: http://download.oracle.com/javase/1.5.0/docs/guide/2d/flags.html