Comment 10 for bug 319714

9.10 / Karmic seems to have this same issue;

jarkko@gandalf:/etc/apt$ sudo synaptic
Traceback (most recent call last):
  File "/usr/bin/software-properties-gtk", line 104, in <module>
    app = SoftwarePropertiesGtk(datadir=data_dir, options=options, file=file)
  File "/usr/lib/python2.6/dist-packages/softwareproperties/gtk/SoftwarePropertiesGtk.py", line 75, in __init__
    SoftwareProperties.__init__(self, options=options, datadir=datadir)
  File "/usr/lib/python2.6/dist-packages/softwareproperties/SoftwareProperties.py", line 83, in __init__
    self.reload_sourceslist()
  File "/usr/lib/python2.6/dist-packages/softwareproperties/SoftwareProperties.py", line 521, in reload_sourceslist
    self.distro.get_sources(self.sourceslist)
  File "/usr/lib/python2.6/dist-packages/aptsources/distro.py", line 90, in get_sources
    raise NoDistroTemplateException("Error: could not find a "
aptsources.distro.NoDistroTemplateException: Error: could not find a distribution template
jarkko@gandalf:/etc/apt$ dpkg -l | grep software-properties-gtk
ii software-properties-gtk 0.71.5 manage the repositories that you install sof
jarkko@gandalf:/etc/apt$