I've seen this error very frequently. Pypanel can't start sometimes. Usually after booting the system.
I am using pypanel + openbox.

pypanelrc version : None
pypanel   version : 2.4

A current pypanelrc example can be found here -
/usr/pkg/lib/python2.4/site-packages/pypanel/pypanelrc

Traceback (most recent call last):
  File "/usr/pkg/bin/pypanel", line 957, in ?
    PyPanel(display.Display())
  File "/usr/pkg/bin/pypanel", line 94, in __init__
    self.getDesktopNames()
  File "/usr/pkg/bin/pypanel", line 360, in getDesktopNames
    desktop.total = self.root.get_full_property(self._DESKTOP_COUNT, 0).value[0]
AttributeError: 'NoneType' object has no attribute 'value'

Regards

Csar Catrin C.
http://mioficina.cjc.cl/