[jQuery] Ajax problem with mac osX

[junior2000]

Hi,
I've a problem with an ajax call only on mac systems. On windows and
linux works well.
In the systems with problem firebug displays that the post request
don't load.
I've used the last jquery and the forms plugin.
Here the script:

Thanks for any suggestion.

<script type="text/javascript" language="JavaScript">
<!--

$(document).ready(function(){

function calcolaCostoNoleggio() {

nSettimane=0;
nMesi=0;
nTipoDurata=$(":radio").fieldValue();
nDurata=$("#durata").val();
nCliente=$("#idc").val();
nProduct=$("#id").val();

$.ajax({ type: "POST", url: "costonoleggio.php", data:
"durata="+nDurata+"&tipo_durata="+nTipoDurata+"&idc="+nCliente
+"&id="+nProduct, dataType: "xml", success: function(xmlData) {


$("#costo").html($("costo",xmlData).text());
abbonamento=$("abbonamento",xmlData).text();
if (abbonamento>2) $("#copertura_abbonamento").html("L'abbonamento non
copre interamente il noleggio");
else $("#copertura_abbonamento").html("L'abbonamento copre interamente
il noleggio");


}
});

}

calcolaCostoNoleggio();



  $("#durata").change(function(event){
calcolaCostoNoleggio();
});


    $("#tipi input").click(function(event){
calcolaCostoNoleggio();
})


});


//-->
</script>