MOUSE_DOWN adds Mouse Up automatically?

ok… I did the following:

added an event Listener to my object:

addEventListener(MouseEvent.MOUSE_DOWN,clickHandler);

didn’t add any other MouseEvent listeners…
still… now the function clickHandler is called at a mouse_up event aswell… :s

in a destroy function, I remove this Event Listener:

removeEventListener(MouseEvent.MOUSE_DOWN,clickHandler);

after I removed the listener the mouse down doesn’t work anymore,
the mouse_up does…

Any solutions, or is this a know error?