Help with error message (TypeError: Error #1006: value is not a function. at Meth...)

Hi all, I get this error message

#1006: value is not a function.
at MethodInfo-43()

I don’t know what the problem is, or where could it be, here is the problem code, but first a brief description:
Every 3 seconds 3 enemies will be created with a random position, the enemies can’t be appearing on top of the other so I check if they collide with any previously added enemies, if they do I assign other random coordinates and check again until there is no collision (I’m using the collision detection kit CDK for the collisions http://coreyoneil.com/portfolio/index.php?project=5).
the first 3 enemies appear correctly but afterwards the error appears and the next time the program enters the generation part the enemies begin appearing in ridiculous numbers.

function mainLoop(event:Event):void{
                
                currentTime = getTimer();
                                
                if(currentTime - timeEnemies >= 3000){
                                                    
                    for(var i:Number = 0; i < enemyWaveNumber; i++){
                        
                        var coordY:Number = 0;
                        var coordX:Number = 0;
                        var noCollision:Boolean = false;
                        
                        // Generate enemies checking if they don't collide
                        while(noCollision == false){
                            var enemigo:Enemy1 = new Enemy1();
                            addChild(enemigo);
                            coordX = Math.random() * 550;
                            coordY = 10 + Math.floor(Math.random()*(200-10+1));
                            enemigo.x = coordX;
                            enemigo.y = coordY;
                            enemigo.gotoAndStop("1");
                            
                            if(enemigos.length > 1){
                                var colisionador:CollisionGroup = new CollisionGroup();
                                colisionador.addItem(enemigo);
                                
                                for(var f:Number = 0; f < enemigos.length(); f++){
                                    var agregame:MovieClip = MovieClip(enemigos[f]);
                                    colisionador.addItem(agregame);
                                }
                                var colisiones:Array = new Array();
                                colisiones = colisionador.checkCollisions();
                                if(colisiones.length == 0){
                                    noCollision = true;
                                    enemigos.push(enemigo);
                                }
                                else{
                                    removeChild(enemigo);
                                    enemigo = null;
                                }
                            }
                            else{
                                enemigos.push(enemigo);
                                noCollision = true;
                            }
                        }
                        
                        timeEnemies = currentTime;
                        
                    }
                    
                    
                }
                else{}
                // move enemies
                
            }

full code and ,fla attached in code.zip, the problem is in Prueba.as (.fla made in flash cs4) (the assets are on the ugly side but there just there for thee tests )