PHP ZipArchive Corrupt in Windows

I am using PHP's ZipArchive class to create a zip file containing photos and then serve it up to the browser for download. Here is my code:

/**
 * Grabs the order, packages the files, and serves them up for download.
 *
 * @param string $intEntryID 
 * @return void
 * @author Jesse Bunch
 */
public static function download_order_by_entry_id($intUniqueID) {

    $objCustomer = PhotoCustomer::get_customer_by_unique_id($intUniqueID);

    if ($objCustomer):

        if (!class_exists('ZipArchive')):
            trigger_error('ZipArchive Class does not exist', E_USER_ERROR);
        endif;

        $objZip = new ZipArchive();
        $strZipFilename = sprintf('%s/application/tmp/%s-%s.zip', $_SERVER['DOCUMENT_ROOT'], $objCustomer->getEntryID(), time());

        if ($objZip->open($strZipFilename, ZIPARCHIVE::CREATE) !== TRUE):

            trigger_error('Unable to create zip archive', E_USER_ERROR);

        endif;          

        foreach($objCustomer->arrPhotosRequested as $objPhoto):

            $filename = PhotoCart::replace_ee_file_dir_in_string($objPhoto->strHighRes);
            $objZip->addFile($filename,sprintf('/press_photos/%s-%s', $objPhoto->getEntryID(), basename($filename)));

        endforeach;

        $objZip->close();

        header('Last-Modified: '.gmdate('D, d M Y H:i:s', filemtime($strZipFilename)).' GMT',  TRUE, 200);
        header('Cache-Control: no-cache', TRUE);
        header('Pragma: Public', TRUE);
        header('Expires: ' . gmdate('D, d M Y H:i:s', time()) . ' GMT', TRUE);
        header('Content-Length: '.filesize($strZipFilename), TRUE);
        header('Content-disposition: attachment; filename=press_photos.zip', TRUE);

        header('Content-Type: application/octet-stream', TRUE);

        ob_start();
        readfile($strZipFilename);
        ob_end_flush();
        exit;

    else:

        trigger_error('Invalid Customer', E_USER_ERROR);

    endif;

}

This code works