JQuery ui - date picker, disabling specific dates

It looks like you're calling datepicker twice on one input. Its kind of hard to follow your code, but if you re-organize it and remove the second datepicker call, everything should work:

<script type="text/javascript">
    var unavailableDates = ["9-3-2012", "14-3-2012", "15-3-2012"];

    function unavailable(date) {
        dmy = date.getDate() + "-" + (date.getMonth() + 1) + "-" + date.getFullYear();
        if ($.inArray(dmy, unavailableDates) == -1) {
            return [true, ""];
        } else {
            return [false, "", "Unavailable"];
        }
    }

    $(function() {
        $("#iDate").datepicker({
            dateFormat: 'dd MM yy',
            beforeShowDay: unavailable
        });

    });
</script>

Check this article: disable-dates-in-datepicker