It seems that issue for me was different login names on my Ubuntu One/Launchpad and /etc/apt/auth.conf files (I was changed my Ubuntu One/Launchpad username). After auth.conf login name was corrected apt- get update show no errors.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1130945 Title: Trying to install steam breaks apt-get update To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/software-center/+bug/1130945/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs