Problems with PHPExcel

I'm trying to modify a excel with php, once I change what I need I'm supposed to save it, once I save it, then the problem arises that when I download it and open it, it tells me what next:

Being that I do not make any change I only open it and I give it to close, it is supposed that I should not show that message because when I change it I keep it. My code is as follows:

    $fecha_inicial = $this->input->post ( 'date_start' );
    $nombre_ruta = $this->input->post ( 'route_name' );
    $archivo = str_replace(" ","_",$this->input->post ( 'name' ));
    $ext = strrchr($archivo, ".");
    $hoja_excel = "./plantillas_excel/".$archivo;
    $this->load->library('excel');

    $inputFileType = PHPExcel_IOFactory::identify($hoja_excel);
    $objReader = PHPExcel_IOFactory::createReader($inputFileType);
    $objPHPExcel = $objReader->load($hoja_excel);
    $objPHPExcel->setActiveSheetIndex(0);
    //Indicamos que se pare en la hoja uno del libro
    $objWorksheet = $objPHPExcel->getActiveSheet();
    $data = $objWorksheet->rangeToArray('A2:N2000');

    $numeroCelda = 1;
    foreach ($data as $row) {
        $numeroCelda++;
        if($row[0]!=null)
        {

            $fecha_nombre = str_replace ("-" , "" , $fecha_inicial );
            //$objWorksheet->getCell('A'.$numeroCelda)->getValue()
            $objWorksheet->SetCellValue('A'.$numeroCelda, $nombre_ruta." ".$fecha_nombre);
            $valDateB = $objWorksheet->getCell('B'.$numeroCelda)->getValue();
            if($valDateB!=null && is_numeric ( $valDateB )){
                    $valB= PHPExcel_Shared_Date::ExcelToPHPObject($valDateB);
                    $valDateB = $valB->format($fecha_inicial.' H:i:s');
                    $objWorksheet->SetCellValue('B'.$numeroCelda, PHPExcel_Shared_Date::PHPToExcel($valDateB));
            }

            $valDateN = $objWorksheet->getCell('N'.$numeroCelda)->getValue();
            if($valDateN!=null && is_numeric ( $valDateN )){
                $valN= PHPExcel_Shared_Date::ExcelToPHPObject($valDateN);
                $valDateN = $valN->format($fecha_inicial.' H:i:s');
                   $objWorksheet->SetCellValue('N'.$numeroCelda, PHPExcel_Shared_Date::PHPToExcel($valDateN));
            }   
        }
        else {
            break;
        }
    }

    $objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, $inputFileType);
    header("Content-Type: application/force-download");
    header("Content-Type: application/application/vnd.ms-excel");
    header("Content-Type: application/download");
    header('Content-Disposition:inline;filename="'.$fecha_nombre.'.xls"');
    header("Content-Transfer-Encoding: binary");
    header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
    header("Pragma: no-cache");
    $objWriter->save('php://output');

If someone knows where I'm watering it, I'd really appreciate it since I'm just getting into php in full ...