Movement Keys not Working - actionscript-3

Question

Nothing is happening when I press the arrow keys, but neither are there any errors: what's wrong with this? If I remove the key press testing it accelerates accordingly...
At this stage I am just trying to move a block around a screen in an inertial manner using the arrow keys. However, this is my first foray into AS3 so I may be going about it in completely the wrong manner.
Any help would be greatly appreciated.
Unit.AS:
package {
import flash.display.MovieClip;
import flash.events.*
import flash.ui.Keyboard
public class Unit extends MovieClip {
var velocityX:Number = 1;
var velocityY:Number = 1;
var accellerationX:Number = 1;
var accellerationY:Number = 1;
public function Unit(){
addEventListener("enterFrame", move);
}
private function move(e:Event){
accellerate()
this.x += velocityX;
this.y += velocityY;
}
private function accellerate(){
if (Key.isDown(Keyboard.UP)){
velocityY += accellerationY;
trace("Accellerating");
}
if (Key.isDown(Keyboard.DOWN)){
velocityY -= accellerationY;
trace("Accellerating");
}
if (Key.isDown(Keyboard.RIGHT)){
velocityX += accellerationX;
trace("Accellerating");
}
if (Key.isDown(Keyboard.LEFT)){
velocityX -= accellerationX;
trace("Accellerating");
}
}
}
}
Key.AS:
package
{
import flash.display.Stage;
import flash.events.Event;
import flash.events.KeyboardEvent;
public class Key {
private static var initialized:Boolean = false;
private static var keysDown:Object = new Object();
public static function initialize(stage:Stage) {
if (!initialized) {
stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressed);
stage.addEventListener(KeyboardEvent.KEY_UP, keyReleased);
stage.addEventListener(Event.DEACTIVATE, clearKeys);
initialized = true;
}
}
public static function isDown(keyCode:uint):Boolean
{
return Boolean(keyCode in keysDown);
}
private static function keyPressed(event:KeyboardEvent):void {
keysDown[event.keyCode] = true;
}
private static function keyReleased(event:KeyboardEvent):void {
if (event.keyCode in keysDown) {
delete keysDown[event.keyCode];
}
}
private static function clearKeys(event:Event):void {
keysDown = new Object();
}
}
}

Answer 1

On your unit constructor function call the initialize(stage) static function.
Key.initialize(stage);