near impossible to move windows on the screen ... just try.
Dwachs is working at the windows. There are also a bug reports to about the same topic in the German forum.
http://www.simutrans-forum.de/forum/thread.php?threadid=5471
http://www.simutrans-forum.de/forum/thread.php?threadid=5469
http://www.simutrans-forum.de/forum/thread.php?threadid=5468
Its a bug in all simutrans version greater than 3371.
In fact, prissi does something there behind the scenes.
Please use nightly version <=3370 for the moment.
Still not finished, but moving and resizing should work better than before.