Klaus,
The Data Browser does hide some useful information, but it can be made to reveal its secrets. In your case if you address the object's x or y properties like this you will get the result that may help:
$.writeln (oObject.Points[0].x); $.writeln (oObject.Points[0].y);
I've not tried to create a polyline yet, but perhaps explicitly referencing x and y will do what you need?
Ian