removeChild problems

[highway81]

Hi,

I am pretty new to AS3 and am trying to build a game based on Pong. I am having trouble however. When a ‘goal’ is scored, i am given the following error:

ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller.
at flash.display:isplayObjectContainer/removeChild()
at Pong/ballPosition()

package {

import flash.display.Sprite;
import flash.display.*;
import flash.events.*;
import flash.text.*;

public class Pong extends MovieClip {
    
    private var paddle:Paddle;
    private var paddle2:Paddle;
    private var ball:Ball;
    private var topLine:Line;
    private var bottomLine:Line;
    public var upArrow, downArrow:Boolean;
    public var upArrow2, downArrow2:Boolean;
    public var spacebarDown:Boolean;
    public var ballOutOfPlay:Boolean;
    public var ballDX:Number;
    public var ballDY:Number;
    public var playerOneScore:Number;
    
    public function Pong() {
        
        //set speed of ball
        ballDX = 10;
        ballDY = 5;
        
        //set score
        playerOneScore = 0;
        
        //set up stage
        showPlayerOneScore.text = ""+playerOneScore;
        showPlayerTwoScore.text = "0";
        
        topLine = new Line();
        addChild(topLine);
        topLine.x = stage.stageWidth/2;
        topLine.y = 43;
        
        bottomLine = new Line();
        addChild(bottomLine);
        bottomLine.x = stage.stageWidth/2;
        bottomLine.y = 393;
        
        paddle = new Paddle();
        addChild(paddle);
        paddle.x = 25;
        paddle.y = 80;
        
        paddle2 = new Paddle();
        addChild(paddle2);
        paddle2.x = 523;
        paddle2.y = 80;
        paddle2.width = 30;
        
        ball = new Ball();
        ball.x = 125;
        ball.y = 80;
        addChild(ball);
        
        //key presses and stage boundary
        stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDownFunction);
        stage.addEventListener(KeyboardEvent.KEY_UP, keyUpFunction);
        stage.addEventListener(Event.ENTER_FRAME, stageBoundary);
        stage.addEventListener(Event.ENTER_FRAME, stageBoundary2);
        
        //animations
        paddle.addEventListener(Event.ENTER_FRAME, movePaddle);
        paddle2.addEventListener(Event.ENTER_FRAME, movePaddle2);
        ball.addEventListener(Event.ENTER_FRAME, moveBall);
        
        //check for paddlecollision
        ball.addEventListener(Event.ENTER_FRAME, hitBall);
        
        // check for goal
        ball.addEventListener(Event.ENTER_FRAME, ballPosition);
        
        if (ballOutOfPlay) {
            removeChild(ball);
        }

    }
    
    // key pressed
    public function keyDownFunction(event:KeyboardEvent):void {
        if (event.keyCode == 65) {
            upArrow = true;
        }
        else if (event.keyCode == 90) {
            downArrow = true;
        }
        else if (event.keyCode == 38) {
            upArrow2 = true;
        }
        else if (event.keyCode == 40) {
            downArrow2 = true;
        }
        else if (event.keyCode == 32) {
            spacebarDown = true;
        }
    }
    
    // key released
    public function keyUpFunction(event:KeyboardEvent):void {
        if (event.keyCode == 65) {
            upArrow = false;
        }
        else if (event.keyCode == 90) {
            downArrow = false;
        }
        else if (event.keyCode == 38) {
            upArrow2 = false;
        }
        else if (event.keyCode == 40) {
            downArrow2 = false;
        }
    }
    
    //move ball
    public function moveBall(event:Event):void {
        if(spacebarDown) {
            ball.x -= ballDX;
            ball.y += ballDY;
        }
    }
    
    // stage boundary
    public function stageBoundary(event:Event):void {
        if (paddle.y <= 80) {
            upArrow = false;
        }
        else if (paddle.y >= 351) {
            downArrow = false;
        }
    }
    
    public function stageBoundary2(event:Event):void {
        if (paddle2.y <= 80) {
            upArrow2 = false;
        }
        else if (paddle2.y >= 351) {
            downArrow2 = false;
        }
    }
    
    //check for goal
    public function ballPosition(event:Event) {
        if (ball.x < 0) {
            ballOutOfPlay = true;
            trace("goal");
            playerOneScore++;
            showPlayerOneScore.text = ""+playerOneScore;
            removeChild(ball);
        }
        
    }
    
    //move paddles
    public function movePaddle(event:Event) {
        if(upArrow) {
            paddle.y -=10;
        }
        else if(downArrow) {
            paddle.y +=10;
        }
        
    }
        
    public function movePaddle2(event:Event) {
        if(upArrow2) {
            paddle2.y -=10;
        }
        else if(downArrow2) {
            paddle2.y +=10;
        }
    }
    
    //check for bouncing ball
    public function hitBall(event:Event) {
        if(ball.hitTestObject(paddle)) {
            //trace("hit");
            ballDX*=-1;
        }
        else if(ball.hitTestObject(paddle2)) {
            //trace("hit2s");
            ballDX*=-1;
        }
        else if(ball.hitTestObject(topLine)) {
            //trace("hitTop");
            ballDY*=-1;
        }
        else if(ball.hitTestObject(bottomLine)) {
            //trace("hitBottom");
            ballDY*=-1;
        }
    }
    
}

}

Any help is greatly appreciated

Thanks

-John