E: The value 'oneiric' is invalid for APT::Default-Release as such a release is not available in the sources E: _cache->open() failed, please report.

[chasmarang]

E: The value 'oneiric' is invalid for APT::Default-Release as such a release is not available in the sources
E: _cache->open() failed, please report.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: synaptic 0.75.9ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-24.38-generic 3.2.16
Uname: Linux 3.2.0-24-generic i686
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu7
Architecture: i386
Date: Thu May 10 02:27:56 2012
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release i386 (20091028.5)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: synaptic
UpgradeStatus: No upgrade log present (probably fresh install)

[Robert Roth (evfool)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug #978821, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Feel free to continue to report any other bugs you may find.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Misaki (myjunkmail311006)]

From http://ubuntuforums.org/showthread.php?p=11403493

The APT::Default-Release identifier is within Synaptic config file at each home directory (for you and root). I have recreated this error by manually editing those files.

Going to /root/.synaptic/synaptic.conf and changing the default distro to precise fixed it for me.