update 12.4 failed due to fetch problem with karmic-backports

W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/karmic-backports/main/source/Sources 404 Not Found [IP: 91.189.92.152 80]
, W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/karmic-backports/restricted/source/Sources 404 Not Found [IP: 91.189.92.152 80]
, W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/karmic-backports/universe/source/Sources 404 Not Found [IP: 91.189.92.152 80]
, W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/karmic-backports/multiverse/source/Sources 404 Not Found [IP: 91.189.92.152 80]
, E:Some index files failed to download. They have been ignored, or old ones used instead.

You need to remove the offending/obsolete lines from your /etc/apt/sources.list file (or whatever file in /etc/apt/sources.lidt.d contains them)/

Please read this:

https://help.ubuntu.com/community/PreciseUpgrades

and this:

https://wiki.ubuntu.com/Releases

Karmic is end-of-life and not supported anymore since April 30, 2011

You cannot upgrade directly from karmic (Ubuntu 9.10) to precise (Ubuntu 12.04)

You can only do a direct upgrade from Ubuntu 10.04 or from Ubuntu 11.10 to Ubuntu 12.04 LTS.