GUI box overlapping when reloading the scene

Uh, this is a really annoying problem. the following script draws a GUI box (the score)on the screen and when the player reaches a certain score, the player is given the option to play the level again. When I click the button to reload the level the GUI box should only be drawn once every time I reload the scene, but when I click the replay button it reloads the scene and draws another box, overlapping the previous one. Does anybody know how to fix the problem? thanks

 #pragma strict
 
 var items = 0.0;
 private var showGUI : boolean = true;
 
 function OnGUI () {
     
     if(showGUI == true)
     {
             GUI.Box(Rect(10, 10, 100, 20), "items: " + items);
             if(items >= 6)
             {
                 win();
             }
             
     }    
     
     else
     {
         showGUI = false;
     }
 }
 
 function win()
 {
     
     GUI.Box(Rect(Screen.width / 2, 5, 100, 20), "You Win!");
     
     if(GUI.Button(Rect(10, 30, 100, 20), "Play Again"))
     {
         Application.LoadLevel(2);
     }
     
     //GUI.Button(Rect(10, 50, 100, 20), "Next Level");
 }