Crash on startup with SystemError in getGamma()

Binary package hint: displayconfig-gtk

Crashes on startup in Ubuntu Feisty. I have a heavily modified xorg.conf which may be causing this.

# displayconfig-gtk
Xlib: extension "XFree86-VidModeExtension" missing on display ":0.0".
Traceback (most recent call last):
  File "/usr/bin/displayconfig-gtk", line 11, in <module>
    app = DisplayConfig("/usr/share/displayconfig-gtk/displayconfig.glade")
  File "/usr/lib/python2.5/site-packages/displayconfiggtk/DisplayConfig.py", line 116, in __init__
    self.xsetup = XSetup(self.xconfigpath)
  File "/usr/lib/python2.5/site-packages/displayconfig/displayconfigabstraction.py", line 387, in __init__
    self._finalizeInit()
  File "/usr/lib/python2.5/site-packages/displayconfig/displayconfigabstraction.py", line 392, in _finalizeInit
    gfxcard._finalizeInit()
  File "/usr/lib/python2.5/site-packages/displayconfig/displayconfigabstraction.py", line 1103, in _finalizeInit
    screen._finalizeInit()
  File "/usr/lib/python2.5/site-packages/displayconfig/displayconfigabstraction.py", line 1620, in _finalizeInit
    (self.redgamma, self.greengamma, self.bluegamma) = self.x_live_screen.getGamma()
  File "/usr/lib/python2.5/site-packages/displayconfig/xf86misc.py", line 55, in getGamma
    return ixf86misc.GetGamma(self.display,self.screenid)
SystemError: error return without exception set

ProblemType: Crash
Architecture: i386
Date: Thu Mar 29 12:35:57 2007
DistroRelease: Ubuntu 7.04
ExecutablePath: /usr/bin/displayconfig-gtk
InterpreterPath: /usr/bin/python2.5
Package: displayconfig-gtk 0.2ubuntu2
PackageArchitecture: i386
ProcCmdline: /usr/bin/python /usr/bin/displayconfig-gtk
ProcCwd: /home/charlie
ProcEnviron:
 SHELL=/bin/bash
 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
 LANG=en_GB.UTF-8
PythonArgs: ['/usr/bin/displayconfig-gtk']
SourcePackage: displayconfig-gtk
Uname: Linux soyo 2.6.20-13-386 #2 Sun Mar 25 00:18:53 UTC 2007 i686 GNU/Linux