By adding the dummy "natty" repo back into sources.list shall fix the problem temporarily
[yohjiubuntu-tv:~]$ cat /etc/apt/sources.list deb http://tw.archive.ubuntu.com/ubuntu natty main universe restricted multiverse -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/842179 Title: Short after upgrade, Synaptic failed to open but apt-get still works To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/synaptic/+bug/842179/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs