Jquery UI Dialog + Datetimepicker

Jquery UI Dialog + Datetimepicker

I'm using Datetimepicker inside the jquery-ui dialog, however it doesn't work, giving me this error:

f is null

this._getInst(d(a)[0]);b.input&&b._sel...entYear))}},_clearDate:function(a){a=

When I use datetimepicker in other pages (without dialog) it works just fine....inside the dialog is a problem...
My code:

$(document).ready(function(){

    // Datepicker
    $('.datepicker').datepicker({
            changeMonth: true,
            changeYear: true,
            showOn: 'button',
      inline: true,
        buttonImage: '/images/calendar.png',
            buttonImageOnly: true
        }, $.datepicker.regional['pt-BR']);

        $('.datepicker').each(function() {
        if(this.value == "01/01/-4712")
        this.value = "";
        });

      $('#novo_movimento').dialog({
      modal: true,
      resizable: false,
      autoOpen: false,
      show: 'drop',
      hide: 'drop',
      title: 'Novo movimento',
      width: 500,
      height: 350,
      closeOnEscape: true,
      buttons: {
        "Cancelar": function(){
          $(this).dialog("close");
        },
        "Salvar": function(){
          $("#new_movimento").submit();
        }
      }
    });
});