Kohana 3.2 + PHPExcel creates empty document when there are more than 31 rows written.

I'm trying to create a simple excel document that contains a 3-column list. (First Name, Last Name, Email Address)

When I output more than 31 rows, a blank excel file is created. Does anyone know how to fix it?

My code below:

    $guests = ORM::factory('guest')
      ->order_by('last_name', 'ASC')
      ->find_all()
  ->as_array(); 

$columns = array('first_name', 'last_name', 'email');


$objPHPExcel = new PHPExcel();

$objPHPExcel->getProperties()
        ->setCreator('Me')
        ->setLastModifiedBy('Me)
        ->setTitle('Guest List')
        ->setSubject('Guest List')
        ->setDescription('Title of Report, run on ' . date('m/d/Y H:i:s'));
$objPHPExcel->createSheet(0);
$objPHPExcel->setActiveSheetIndex(0);

    foreach($guests as $row => $guest) {
        $source = array();
        $column = 0;
        $next_row = $objPHPExcel->getActiveSheet()->getHighestRow();

        foreach($guest->as_array() as $column_name => $data)  {
            if(in_array($column_name, $columns)) {

              $objPHPExcel->getActiveSheet()
                ->setCellValueByColumnAndRow($column, $next_row+1, $data);  

              $column++;
              // unset($data);
            }
        }

    }

    $objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel5');   
    $this->response->body($objWriter->save('php://output'));
    $this->response->send_file(TRUE, 'GuestList.xls');

Kohana has a hard time handling the rendered file using the send_file() method, so write the file to disk using the built-in method from PHPExcel. Then use Kohana to deliver the saved file as a download.

$objWriter = new PHPExcel_Writer_Excel2007($objPHPExcel);
$objWriter->save($filename, 'EXCEL2007');
$this->response->send_file( DOCROOT.$filename );