Safari 3.2.1 and $.ajax POST doesn't work

Safari 3.2.1 and $.ajax POST doesn't work

Hello to the ng;

i have a form that should be submitted via ajax; it works of ff and ie, but doesn't in safari 3.2.1.
I've simplified every page to isolate the problem:

The html:
<form name="form" id="richiestapreventivo" action="" method="POST" enctype="multipart/form-data">
                <fieldset>
                        <legend>Richiesta preventivo</legend>   
                        <ol id="datiazienda">
                                <li>
                                        <label>ragione sociale</label>
                                        <input name="ragionesociale" id="ragionesociale" size="20" class="required" value="<?php if (isset($_SESSION['ragionesociale'])) echo $_SESSION['ragionesociale']; ?>"/>
                                </li>
                       
                        </ol>
                       
                        <button type="submit" class="button" id="invia">invia richiesta</button>
                </fieldset>
        </form>


The js:
<script type="text/javascript" charset="utf-8">
        $(document).ready(function(){
  $('form#richiestapreventivo').bind("submit", function() {
                                $.ajax({
                                        type: "POST",
                                        url: "bin/sendmail2.php"   
                                });   
                });
        });
</script>


sendmail2.php:
<?php
error_log("ok");
?>


After some days of searching and debugging, I cannot get it out..
Could you help me?

Alex - italy