ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller.

          at flash.display::DisplayObjectContainer/removeChild()

          at Application2_fla::MainTimeline/frame9()

          at flash.display::MovieClip/gotoAndStop()

          at Function/<anonymous>()

What does this mean please?

Frame 9 coding

flash.display.MovieClip

stop();

stage.removeChild(Characters1); //Remove Child Characters1 From Stage

stage.removeChild(Characters2); //Remove Child Characters2 From Stage

var playerScoreScreen = int(playerFinalScore.text); //Convert To Integer

var computerScoreScreen = int(computerFinalScore.text); //Convert To Integer

this.addEventListener(Event.ENTER_FRAME, overallWinner); //Add Enter Frame Event Listener

function overallWinner(event:Event):void

{

          //If playerFinalScore Is Equal To computerFinalScore Do The Following

          if (int(playerFinalScore.text) == int(computerFinalScore.text))

          {

                    announceWinner.text = "Draw"; //Display In The announceWinner Text Box That It's A Draw

                    trace("Draw"); //Trace That It's A Draw

          }

          //If playerFinalScore Is Greater Than computerFinalScore Do The Following

          if(int(playerFinalScore.text) > int(computerFinalScore.text))

          {

                    announceWinner.text = "Player Wins"; //Display In The announceWinner Text Box That The Player Wins

                    trace("Player Wins"); //Trace That The Player Wins

          }

          //Else Do The Following

          else

          {

                    announceWinner.text = "Computer Wins"; //Display In The announceWinner Text Box That The Computer Wins

                    trace("Computer Wins"); //Trace That The Computer Wins

          }

}

playAgain.addEventListener(MouseEvent.CLICK, retry);

function retry(event:MouseEvent)

{

          gotoAndStop(8);

}

//Adding An Event Listener To The Button playAgain

//Function retry Runs gotoAndStop(8); Which Is Go To And Stop At Frame 8 Allowing You To Play The Application Game Again

displayCredits.addEventListener(MouseEvent.CLICK, credits);

function credits(event:MouseEvent)

{

          gotoAndPlay(10);

}

//Adding An Event Listener To The Button creditsButton

//Function retry Runs gotoAndStop(10); Which Is Go To And Stop At Frame 10 Allowing You To View The Credits