jquery - IE <9 doesnot go throught one function

Question

I have some problems with IE less then 9 version... It can't go throught one function

if (g_pk.length == 11 || g_pk.length == 12) {
    if (check_pc(g_pk) == 0) {
        $.ajax
        ({
            data: {
                action: 'search_full_pk',
                pk: g_pk
            },
            success: function (a) {

                //////////////////////////////////////////
                //on filial select
                $('td#filial_list')
                    .on('click', 'div', select_by_filial);
                //on patient aelect
                $('td#patient_list')
                    .on('click', 'div', select_by_patient);
                //////////////////////////////////////////

                if (a.errors.length > 0) {
                    txtError.show();
                    txtError.val(a.errors);

                    $('#filial_list').hide();
                    $('#result_list').hide();
                    $('#patient_list').hide();
                    $('#year_list').hide();

                    return;
                }
                $('#filial_list').show();
                $('#result_list').show();
                $('#patient_list').show();
                $('#year_list').show();

                $('#filial_list').html(a.result.filiali_html);
                $('#patient_list').html(a.result.pacient_div);
                $('#result_list').html(a.result.table);
                $('#year_list').html(a.result.data_div);
                $('#btnReset').show();
            }
        });
    }
    else {
        txtError.show();
        txtError.val('<?php echo false_pk ?>');
        $('#btnReset').show();
    }
}
else {
    txtError.show();
    $('#btnReset').show();
    txtError.val('<?php echo false_pk ?>');
}

and I don't know why it is...=( because if I test this function on IE 9 or higher it's works nice...

any sugestions?

UPD 1 here is an ajax setup:

$.ajaxSetup
({
    url: "ajax.php",
    type: "POST",
    dataType: "json"
});