jquery dialog runtime error on IE (0x800a01b6)

My javascript method that opens my jquery dialog when i save something in my app is not working anymore.

MessageBox: function (titulo, mensagem) {
        $('#message-box')
                .attr('title', titulo)
                .html(mensagem)
                .dialog({
                    modal: true,
                    buttons: {
                        "Ok": function () {
                            $(this).dialog("close");
                        }
                    }
                });
    },

now I'm getting this error only on IE:

“0x800a01b6 - Microsoft JScript runtime error: Object doesn't support this property or method: 'dialog'”

In other browsers (firefox and Chrome) works perfect.