Bug tracker web interface sometimes records submissions twice (with firefox)

[Simon 'corecode' Schubert]

Does somebody know why firefox still allows the form to be submitted twice?  The page contains this code:

<script type="text/javascript">
submitted = false;
function submit_once() {
   if (submitted) {
       alert("Your request is being processed.\nPlease be patient.");
       event.returnValue = 0;    // work-around for IE
       return 0;
   }
   submitted = true;
   return 1;
}
function help_window(helpurl, width, height) {
   HelpWin = window.open('http://bugs.dragonflybsd.org/' + helpurl, 'RoundupHelpWindow', 'scrollbars=yes,resizable=yes,toolbar=no,height='+height+',width='+width);
}
</script>
. ..

<form method="POST" name="itemSynopsis"
     onsubmit="return submit_once()"
     enctype="multipart/form-data" action="issue1200">
. ..