[ubuntu] Software Updater Error

When ever I try to get the latest updates, including trying to upgrade to 13.04, I get this Internet error:

W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/...source/Sources 404 Not Found [IP: 91.189.91.13 80]
, W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/...source/Sources 404 Not Found [IP: 91.189.91.13 80]
, W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/...source/Sources 404 Not Found [IP: 91.189.91.13 80]
, W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/...source/Sources 404 Not Found [IP: 91.189.91.13 80]
, W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/...-i386/Packages 404 Not Found [IP: 91.189.91.13 80]
, W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/...-i386/Packages 404 Not Found [IP: 91.189.91.13 80]
, W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/...-i386/Packages 404 Not Found [IP: 91.189.91.13 80]
, W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/...-i386/Packages 404 Not Found [IP: 91.189.91.13 80]
, W:Failed to fetch http://ppa.launchpad.net/screenlets/...source/Sources 404 Not Found
, W:Failed to fetch http://ppa.launchpad.net/screenlets/...-i386/Packages 404 Not Found
, E:Some index files failed to download. They have been ignored, or old ones used instead.

What might be causing this error? My Internet works fine otherwise.

Spike