Ubuntu Tweak crashes on startup: with libnotify init error

[SpeedyWizard]

The error message:

Traceback (most recent call last):
  File "ubuntu-tweak.py", line 75, in <module>
    launcher = TweakLauncher()
  File "ubuntu-tweak.py", line 42, in __init__
    from mainwindow import MainWindow
  File "/usr/share/ubuntu-tweak/mainwindow.py", line 171, in <module>
    from sourceeditor import SourceEditor
  File "/usr/share/ubuntu-tweak/sourceeditor.py", line 27, in <module>
    from thirdsoft import refresh_source
  File "/usr/share/ubuntu-tweak/thirdsoft.py", line 41, in <module>
    from common.notify import notify
  File "/usr/share/ubuntu-tweak/common/notify.py", line 10, in <module>
    notify = Notify()
  File "/usr/share/ubuntu-tweak/common/notify.py", line 6, in __init__
    sys.exit (1)
NameError: global name 'sys' is not defined

System: Ubuntu 9.10
WM: Awesome