pyqgis - Buttons (Ok, Cancel) disappearing in "Apri Modulo" from Attribute Table in QGIS

QGIS 2.0 has changed the visualisation of a form opened from the attribute table: instead of opening the form in a separate window, the form is opened in the same one. This is not a problem, but all the buttons disappear...

I created my own form with Qt4 and all the logic with PyQt and the majority of the constraints are associated to the Ok button: now my logic is no longer useful.

Is it possible to re-enable these buttons in QGIS 2.0.1?

I copy here part of my code, maybe someone can help me.

from PyQt4.QtCore import *  
from PyQt4.QtGui import *  
from definizioni import *

myDialog = None
denominazione = None
denominazioneCheck = None

def formOpen(dialog,layerid,featureid):
  global myDialog

  myDialog = dialog

  global denominazione, denominazioneCheck
  denominazione = myDialog.findChild(QLineEdit,"denominazione")
  denominazione.textChanged.connect(denominazione_onTextChanged)
  if (denominazione.text() == "NULL"):
    denominazione.setText("")
  else:
    temp = denominazione.text()
    denominazione.setText("null")

    denominazione.setText(temp)

  buttonBox = myDialog.findChild(QDialogButtonBox,"buttonBox")
  # Disconnect the signal that QGIS has wired up for the dialog to the button box.
  buttonBox.accepted.disconnect(myDialog.accept)
  # Wire up our own signals.
  buttonBox.accepted.connect(validate)
  buttonBox.rejected.connect(myDialog.reject)
  self.connect(buttonBox, SIGNAL("accepted()"), self.accept)


def denominazione_onTextChanged(text):
  global denominazioneCheck

  if not validateStringNotNull(text):
    denominazione.setStyleSheet("background-color: rgba(255, 107, 107, 150);")
    denominazioneCheck = -2
  else:
    if not validateAlpha(text):
      denominazione.setStyleSheet("background-color: rgba(255, 107, 107, 150);")
      denominazioneCheck = -1

    else:
      denominazione.setStyleSheet("")
      denominazioneCheck = 1

# Valido la form
def validate():
  if denominazioneCheck == -2:
    messageBoxErrore(myDialog,"La denominazione di un comune non puo' essere vuota")
  else:
    if denominazioneCheck == -1:

      messageBoxErrore(myDialog,"La denominazione di un comune non puo' contenere numeri")
    else:
      # Return the form as accepted to QGIS.
      myDialog.accept()

I need that the field of the form respect some constraints, as you can see.

In case that constraints are not fulfilled I don't want that the record is stored in the database (I don't want accept() signal is called!).