The problem:
You're using Flash 10's native 3-D API and notice the projection goes a little skewiff when resizing the window.
The solution:
You need to reset the stage's projection centre on stage resize, like so...
var centre:Point = new Point(stage.stageWidth/2, stage.stageHeight/2);
root.transform.perspectiveProjection.projectionCenter = centre;
root.transform.perspectiveProjection.projectionCenter = centre;
Tags: 3D, AS3, Flash 10, howto, source code