edit o2m in form mode error

[Ferdinand]

trying to edit fiscal years / periods
open o2m periods with switch (works with popup)

MSG underlying C/C++ object has been deleted: File "/usr/lib64/python2.5/site-packages/Koo/View/Form/FormView.py", line 165, in updateDisplay
    self.widgets[name].load(self.record)
  File "/usr/lib64/python2.5/site-packages/Koo/Fields/AbstractFieldWidget.py", line 250, in load
    self.display()
  File "/usr/lib64/python2.5/site-packages/Koo/Fields/AbstractFieldWidget.py", line 241, in display
    self.refresh()
  File "/usr/lib64/python2.5/site-packages/Koo/Fields/AbstractFieldWidget.py", line 120, in refresh
    self.setReadOnly( self._readOnly )
  File "/usr/lib64/python2.5/site-packages/Koo/Fields/Calendar/Calendar.py", line 72, in setReadOnly
    self.uiDate.setReadOnly( value )