I get this after the Update Manager said "Check your Internet Connection"
W:Failed to fetch http://extras.ubuntu.com/ubuntu/dists/quantal/main/source/Sources 502 Bad Request [IP: 91.189.92.152 80]
, W:Failed to fetch http://extras.ubuntu.com/ubuntu/dists/quantal/main/binary-i386/Packages 502 Bad Request [IP: 91.189.92.152 80]
, E:Some index files failed to download. They have been ignored, or old ones used instead.