Just for the record, I'd just encountered this problem on a Linux Mint box and the 'Workaround' of the 'Bug description' has solved it:
$ uname -a Linux 3.2.0-58-generic #88-Ubuntu SMP Tue Dec 3 17:37:58 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux $ cat /etc/linuxmint/info RELEASE=13 CODENAME=maya EDITION="MATE 64-bit" DESCRIPTION="Linux Mint 13 Maya" DESKTOP=MATE TOOLKIT=GTK Thanks a lot! -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to apt in Ubuntu. https://bugs.launchpad.net/bugs/24061 Title: GPG error with apt-get/aptitude/update-manager behind proxy (BADSIG 40976EAF437D05B5) Status in apt package in Ubuntu: Fix Released Status in update-manager package in Ubuntu: Won't Fix Status in apt source package in Precise: Fix Released Status in update-manager source package in Precise: Won't Fix Status in apt source package in Quantal: Fix Released Status in update-manager source package in Quantal: Won't Fix Bug description: I keep getting this when i launch the update manager. W: GPG error: http://archive.ubuntu.com breezy-updates Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmas...@ubuntu.com> How can I fix it? *********** WORKAROUND: ---------- Run the following commands(saves a backup of the old lists and creates a new lists folder) and the BADSIG error does not occur : $ cd /var/lib/apt $ sudo mv lists lists.old $ sudo mkdir -p lists/partial $ sudo apt-get update *********** comment from Rolf Leggewie: This is due to cache inconsistencies and thus is not necessarily a bug in Ubuntu at all. But I hope the fine devs can find a way to better deal with broken proxies. This is a very visible issue, a large number of internet connections are behind proxies and the users cannot do anything about it. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/apt/+bug/24061/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp