Problem animating a Sprite via Tween Class

Seasons Greetings all!

I am having a problem figuring out how to animate a Sprite using the Tween Class.

The code simply places a 550 x 350 box on the center of the stage.
When tested, the swf displays the following error,

[COLOR=DarkRed]1118: Implicit coercion of a value with static type flash.display:Sprite to a possibly unrelated type flash.display:MovieClip.

[/COLOR]My code is listed below.

[COLOR=DarkRed][COLOR=Black]package {

import flash.display.Sprite;
import fl.transitions.*;
  import fl.transitions.easing.*;

public class BasicInterface extends Sprite {
    var ContentBox:Sprite;
    public function BasicInterface () {
    private function init():void {
        ContentBox = new Sprite();
        addChild(ContentBox);, 0xffffff, .5);, .15);, 0, 550, 350);;
        ContentBox.x = 240;
        ContentBox.y = 194.5;
        ContentBox.addEventListener(Event.ENTER_FRAME, onEnterFrm);
    private function onEnterFrm(event:Event):void {
        TransitionManager.start (ContentBox, {type:Zoom, direction:0, duration:1.5, easing:Strong.easeOut, startPoint:10});