Error running update-manager (12.04)

[Markus_Wiederkehr]

When I start update-manager I see the error below. I tried apt-get update && apt-get upgrade but that did not help. Also tried to apt-get install --reinstall update-manager, aptdeamon, aptdeamon-data and python2.7.

Any ideas?

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04.4 LTS
Release: 12.04
Codename: precise

$ update-manager
Traceback (most recent call last):
File "/usr/bin/update-manager", line 115, in <module>
app = UpdateManager(data_dir, options)
File "/usr/lib/python2.7/dist-packages/UpdateManager/UpdateManager.py", line 280, in __init__
self.install_backend = backend.get_backend(self.window_main)
File "/usr/lib/python2.7/dist-packages/UpdateManager/backend/__init__.py", line 48, in get_backend
from InstallBackendAptdaemon import InstallBackendAptdaemon
File "/usr/lib/python2.7/dist-packages/UpdateManager/backend/InstallBackendAptdaemon.py", line 5, in <module>
from aptdaemon import client, errors
File "/usr/lib/python2.7/dist-packages/aptdaemon/client.py", line 70, in <module>
class MemoizedMixIn(MemoizedTransaction, GObject.GObjectMeta):
File "/usr/lib/python2.7/dist-packages/gi/module.py", line 316, in __getattr__
return getattr(self._introspection_module, name)
File "/usr/lib/python2.7/dist-packages/gi/module.py", line 135, in __getattr__
self.__name__, name))
AttributeError: 'gi.repository.GObject' object has no attribute 'GObjectMeta'

[oldos2er]

Try
sudo apt-get update && sudo apt-get dist-upgrade

[Markus_Wiederkehr]

I have tried dist-upgrade, two probably unrelated packages were updated (nvidia-304 and nvidia-settings-304). Unfortunately the problem still persists. Any other ideas?

[Markus_Wiederkehr]

SOLVED: I had a couple of packages that were 'newer than version in archive', python-gi among those. I manually downgraded the packages and now update-manager is working again.