"System Settings -> Monitor & Display" does not work

I use Kubuntu/Feisty on a IBM T60 laptop with an external monitor (dual head). After modifying the display config the System Setting -> Monitor & Display does no longer work. It says:
  The module Monitor & Display could not be loaded

The output of
   kcmshell displayconfig
is listed below. It seems to be a problem with a missing "screenconfig" property - or maybe I'm wrong.

X Error: BadDevice, invalid or uninitialized input device 154
  Major opcode: 145
  Minor opcode: 3
  Resource id: 0x0
Failed to open device
X Error: BadDevice, invalid or uninitialized input device 154
  Major opcode: 145
  Minor opcode: 3
  Resource id: 0x0
Failed to open device
Traceback (most recent call last):
  File "<string>", line 8, in kcontrol_bridge_create_displayconfig
  File "/var/lib/python-support/python2.5/displayconfig.py", line 1698, in create_displayconfig
    return DisplayApp(parent, name)
  File "/var/lib/python-support/python2.5/displayconfig.py", line 441, in __init__
    self.xsetup = XSetup(self.xconfigpath)
  File "/var/lib/python-support/python2.5/displayconfigabstraction.py", line 387, in __init__
    self._finalizeInit()
  File "/var/lib/python-support/python2.5/displayconfigabstraction.py", line 392, in _finalizeInit
    gfxcard._finalizeInit()
  File "/var/lib/python-support/python2.5/displayconfigabstraction.py", line 1103, in _finalizeInit
    screen._finalizeInit()
  File "/var/lib/python-support/python2.5/displayconfigabstraction.py", line 1553, in _finalizeInit
    if self.x_live_screen is not None and self.x_live_screen.resolutionSupportAvailable():
  File "/var/lib/python-support/python2.5/xf86misc.py", line 54, in resolutionSupportAvailable
    return self.screenconfig is not None
AttributeError: 'XF86Screen' object has no attribute 'screenconfig'
Error in sys.excepthook:
Traceback (most recent call last):
  File "/var/lib/python-support/python2.5/apport_python_hook.py", line 44, in apport_excepthook
    binary = os.path.realpath(os.path.join(os.getcwdu(), sys.argv[0]))
AttributeError: 'module' object has no attribute 'argv'

Original exception was:
Traceback (most recent call last):
  File "<string>", line 8, in kcontrol_bridge_create_displayconfig
  File "/var/lib/python-support/python2.5/displayconfig.py", line 1698, in create_displayconfig
    return DisplayApp(parent, name)
  File "/var/lib/python-support/python2.5/displayconfig.py", line 441, in __init__
    self.xsetup = XSetup(self.xconfigpath)
  File "/var/lib/python-support/python2.5/displayconfigabstraction.py", line 387, in __init__
    self._finalizeInit()
  File "/var/lib/python-support/python2.5/displayconfigabstraction.py", line 392, in _finalizeInit
    gfxcard._finalizeInit()
  File "/var/lib/python-support/python2.5/displayconfigabstraction.py", line 1103, in _finalizeInit
    screen._finalizeInit()
  File "/var/lib/python-support/python2.5/displayconfigabstraction.py", line 1553, in _finalizeInit
    if self.x_live_screen is not None and self.x_live_screen.resolutionSupportAvailable():
  File "/var/lib/python-support/python2.5/xf86misc.py", line 54, in resolutionSupportAvailable
    return self.screenconfig is not None
AttributeError: 'XF86Screen' object has no attribute 'screenconfig'