TokenMismatchException with uploadify on firefox

Hi,

i'm using the plugin js "uploadify". It's work on google chrome but with firefox, i get "error 500". After some research i found the problem comes from Csrf token (middleware VerifyCsrfToken). I dont understand why it's work on chrome and dont on firefox.

My jquery script to call uploadify plugin is

<script type="text/javascript">
        <?php $timestamp = time();?>
        $(function() {
            $('#file_upload').uploadify({
                'formData'     : {
                    'method' : 'post',
                    'timestamp' : '{!! $timestamp !!}',
                    '_token'     : '{!! csrf_token() !!}'
                },
                'swf'      : '{!!asset("js/uploadify/uploadify.swf")!!}',
                'uploader' : '{!! asset("uploadify")!!}',
                'buttonText' : 'Votre logo'
            });
        });
    </script>

Thx for your help.

PS : sorry for bad english.

PS2 : Laravel 5.0