urlloader, not getting answer

hi, i have this (more or less):

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var loader_grabar_imagen:URLLoader = new URLLoader();

loader_grabar_imagen.dataFormat = URLLoaderDataFormat.VARIABLES;

function grabar_bd_imagen(_cadena:Array):void {

(...) // do some stuff

    var _enviar:URLVariables = new URLVariables("dibujo="+_convertido);
    var _request:URLRequest = new URLRequest(url_grabar_dibujos);
    _request.method = URLRequestMethod.POST; // POST, ya que por el tamaño del dibujo como string no pasa por GET
    _request.data = _enviar;
    //
    try
    {
        loader_grabar_imagen.load(_request);
    }
    catch (error:Error)
    {
        confirmar_NO_grabar();
    }
}

function grabar_resultado(event:Event):void {

    gotoAndStop("some_frame")
}

loader_grabar_imagen.addEventListener(Event.COMPLETE, grabar_resultado);

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in summary: i declare an urlloader. there is a function that tells it to 'load'. there is also another function which is set as 'event.complete' for that urlloader, which should run when that thing finishes. since the first sentende in the complete handler is a goto, it does not depend of the answer per se, but just that ot gets an answer, or that the event is triggered and the handler is called. if it 'completes loading', it should call the handler, thats all.

the problem: is not happening. there is no answer, and there is a block when the loader starts the query to avoid changes meanwhile, it does not get any answer (it does not jump to the frame).. any pointers?

tnx