Custom Cursor

hi,
Ive got a crosshair cursor as part of my game, its loaded in on frame 4 which is where you shoot the targets. It all works fine, then wen i go to the next frame which is the scoreboard it goes back to the pointer fine. But in the output field in getting the following error:

TypeError: Error #1009: Cannot access a property or method of a null object reference. at TargetPractise_fla::MainTimeline/redrawCursor( [TargetPractise_fla.MainTimeline::frame4:7]

My code for the cursor is:

stage.addEventListener(MouseEvent.MOUSE_MOVE, redrawCursor);
stage.addEventListener(Event.MOUSE_LEAVE, hideCursor);
Mouse.hide();

function redrawCursor(event:MouseEvent):void
{
crosshair.visible = true;
crosshair.x = event.stageX;
crosshair.y = event.stageY;
}

function hideCursor(event:Event):void
{
crosshair.visible = false;
}

Thanks in advance

EDIT: Ive got the code for the cursor added in the actions for the frame that it on, if that makes any difference.