Dialog buttons are giving error in IE6

Dialog buttons are giving error in IE6


I am getting an error when I try to open this dialog:
    $("#add_todo_form_div").dialog({
        modal: true,
        autoOpen: true,
        width: 740,
        height: 350,
        overlay:
        {
            opacity: 0.5,
            background: "black"
        },
        buttons:
        {
            "Save": function() {
                add_new_todo();
            },
            "Cancel": function() {
                $(this).dialog("destroy");
            }
        }
    });
If I comment out the "buttons:" section everything works fine except
for the height issue that I talked about in my previous post.