How can I get this imported MouseMotionListener to work again?

Question

I made a JPanel with a mouse listener, a mouse motion listener and a scroll listener. And I have a JFrame that switches between JPanels like so:

    //tile is a JPanel
    //"this" is a JFrame

            tile.removeAll();
            tile=tree.getCurrentNode().getContent().panel;
            this.add(tile);
            this.revalidate();
            tile.requestFocus();

Now when I switch out the old JPanel for the one with mouse listeners some weird things start to happen. The mouse listener and the scroll listener still work but the mouse motion listener doesn't get called anymore. I even get a nullpointer exception when I try getMousePosition() from within the JPanel.