ReferenceError: Error #1069

Hi guys
I am getting reference error which is breaking my code. In my code i have drag gable movieclip which when crossed some coordinates is going to call external UIloader (containing external SWF) on the main stage. I can create multiple instances of UIloader by dragging same movie multiple times.(I am providing the option of dragging and dropping movieClip as well as UIloader too). Now when i am trying to drop movieclip on already created UIloader I am getting this error which is breaking my code. “ReferenceError: Error #1069: Property index not found on flash.display.Stage and there is no default value.”

Actually I have 2 drag and drop functions(on mousedown and mouse up) in my program. One for movieClip drag& drop and other for UILoader drag & drop. It seems like when i am dropping my movieclip on already existing UIloader, drop function of UIloader ( instead of MovieClip) has been called . I am not sure how to fix that.
Any help will be highly appreciated.
I have made everything in AS 3.0 without my custom classes. Attached is the code to make things little clear.
Thanks
Anuj
/Code for movieDrop/

function CamStopDragTN(event:MouseEvent):void
{
var CameraStartDrag=event.currentTarget;

        if ((CameraStartDrag.x>BoundedX) && (CameraStartDrag.y>BoundedY1) &&(CameraStartDrag.y<BoundedY2) &&
            (CameraStartDrag!=null) )
       
        {
            
            CameraStartDrag.stopDrag();    
            var UIcontainer:DisplayObject=CreateUILoaderObject(num);
            UIcontainer.x=mouseX-UIcontainer.width/2;
            UIcontainer.y=mouseY-UIcontainer.height/2;
            
            
            CameraStartDrag.x=x1;
            CameraStartDrag.y=y1;                                
         
        } 

/*Code for UILoader Drop
function dropUILoader(e:MouseEvent):void
{

        if(e.target is UILoader)
        {
            if(mouseY<746)
            {           
  
            var myUILoader:UILoader = e.target as UILoader;        
            
        
            myUILoader.stopDrag();
            myUILoader.mouseChildren=false;

            myUILoader.x=mouseX-myUILoader.width/2-23;
            myUILoader.y=mouseY-myUILoader.height/2-42;
            
          
                    
        else 
        {
            myUILoader.unload();
            container.removeChild(myUILoader);
        
        }
        }
    }