Fail to upgrade due to network/server problem

The easiest solution to that problem is to download the .iso image of 12.04.1 LTS and burn in to a CD/DVD or USB . Boot from there and install Ubuntu from scratch.

Of course you must backup first all your sensitive data because everything will be lost.
Ubuntu 12.04 LTS has a 5 years of support and for that you will not be forced to upgrade again for next 5 years (until April 2017) if you don't want.

So
Download the iso from here:
http://releases.ubuntu.com/precise/

Follow a guide on how to make a bootable Usb-stick , for example you can use Unetbootin:
http://unetbootin.sourceforge.net/

Backup your personal data to an external HDD.

Configure your BIOS to boot first from USB-stick .
Boot with usb-stick attached and a Ethernet cable (more stable connection than WiFi) and install Ubuntu 12.04.1 LTS.

Enjoy !

Thanks

What is the output of:

sudo apt-get update

Thanks

Hi,
there it is:

Ign http://ubuntu.sth.sze.hu oneiric InRelease
Ign http://ubuntu.sth.sze.hu oneiric-updates InRelease
Ign http://ubuntu.sth.sze.hu oneiric-backports InRelease
Ign http://archive.canonical.com oneiric InRelease
Hit http://packages.medibuntu.org oneiric InRelease
Ign http://archive.ubuntu.com maverick-backports InRelease
Ign http://extras.ubuntu.com oneiric InRelease
Ign http://ubuntu.sth.sze.hu oneiric-security InRelease
Hit http://ubuntu.sth.sze.hu oneiric Release.gpg
Hit http://archive.canonical.com oneiric Release.gpg
Ign http://security.ubuntu.com oneiric-security InRelease
Get:1 http://ubuntu.sth.sze.hu oneiric-updates Release.gpg [198 B]
Hit http://ubuntu.sth.sze.hu oneiric-backports Release.gpg
Ign http://archive.ubuntu.com maverick-backports Release.gpg
Get:2 http://extras.ubuntu.com oneiric Release.gpg [72 B]
Hit http://archive.canonical.com oneiric Release
Ign http://archive.ubuntu.com maverick-backports Release
Get:3 http://ubuntu.sth.sze.hu oneiric-security Release.gpg [198 B]
Hit http://extras.ubuntu.com oneiric Release
Get:4 http://security.ubuntu.com oneiric-security Release.gpg [198 B]
Hit http://packages.medibuntu.org oneiric/free i386 Packages
Hit http://archive.canonical.com oneiric/partner Sources
Hit http://ubuntu.sth.sze.hu oneiric Release
Get:5 http://ubuntu.sth.sze.hu oneiric-updates Release [40.8 kB]
Ign http://archive.ubuntu.com maverick-backports/main i386 Packages/DiffIndex
Hit http://extras.ubuntu.com oneiric/main Sources
Hit http://archive.canonical.com oneiric/partner i386 Packages
Ign http://archive.canonical.com oneiric/partner TranslationIndex
Ign http://archive.ubuntu.com maverick-backports/restricted i386 Packages/DiffIndex
Ign http://archive.ubuntu.com maverick-backports/universe i386 Packages/DiffIndex
Ign http://archive.ubuntu.com maverick-backports/multiverse i386 Packages/DiffIndex
Ign http://archive.ubuntu.com maverick-backports/main TranslationIndex
Ign http://archive.ubuntu.com maverick-backports/multiverse TranslationIndex
Ign http://archive.ubuntu.com maverick-backports/restricted TranslationIndex
Ign http://archive.ubuntu.com maverick-backports/universe TranslationIndex
Get:6 http://security.ubuntu.com oneiric-security Release [40.8 kB]
Hit http://extras.ubuntu.com oneiric/main i386 Packages
Ign http://extras.ubuntu.com oneiric/main TranslationIndex
Hit http://packages.medibuntu.org oneiric/non-free i386 Packages
Hit http://ubuntu.sth.sze.hu oneiric-backports Release
Get:7 http://ubuntu.sth.sze.hu oneiric-security Release [40.8 kB]
Hit http://ubuntu.sth.sze.hu oneiric/main Sources
Hit http://ubuntu.sth.sze.hu oneiric/restricted Sources
Hit http://ubuntu.sth.sze.hu oneiric/universe Sources
Hit http://ubuntu.sth.sze.hu oneiric/multiverse Sources
Hit http://ubuntu.sth.sze.hu oneiric/main i386 Packages
Ign http://packages.medibuntu.org oneiric/free TranslationIndex
Hit http://ubuntu.sth.sze.hu oneiric/restricted i386 Packages
Hit http://ubuntu.sth.sze.hu oneiric/universe i386 Packages
Hit http://ubuntu.sth.sze.hu oneiric/multiverse i386 Packages
Hit http://ubuntu.sth.sze.hu oneiric/main TranslationIndex
Hit http://ubuntu.sth.sze.hu oneiric/multiverse TranslationIndex
Hit http://ubuntu.sth.sze.hu oneiric/restricted TranslationIndex
Hit http://ubuntu.sth.sze.hu oneiric/universe TranslationIndex
Get:8 http://ubuntu.sth.sze.hu oneiric-updates/main Sources [167 kB]
Get:9 http://security.ubuntu.com oneiric-security/restricted i386 Packages [4,062 B]
Ign http://packages.medibuntu.org oneiric/non-free TranslationIndex
Get:10 http://ubuntu.sth.sze.hu oneiric-updates/restricted Sources [3,349 B]
Get:11 http://ubuntu.sth.sze.hu oneiric-updates/universe Sources [69.5 kB]
Get:12 http://security.ubuntu.com oneiric-security/main i386 Packages [239 kB]
Get:13 http://ubuntu.sth.sze.hu oneiric-updates/multiverse Sources [3,703 B]
Ign http://archive.canonical.com oneiric/partner Translation-en_US
Get:14 http://ubuntu.sth.sze.hu oneiric-updates/main i386 Packages [432 kB]
Ign http://extras.ubuntu.com oneiric/main Translation-en_US
Ign http://archive.canonical.com oneiric/partner Translation-en
Ign http://extras.ubuntu.com oneiric/main Translation-en
Err http://archive.ubuntu.com maverick-backports/main i386 Packages
  404 Not Found [IP: 91.189.92.200 80]
Err http://archive.ubuntu.com maverick-backports/restricted i386 Packages
  404 Not Found [IP: 91.189.92.200 80]
Err http://archive.ubuntu.com maverick-backports/universe i386 Packages
  404 Not Found [IP: 91.189.92.200 80]
Err http://archive.ubuntu.com maverick-backports/multiverse i386 Packages
  404 Not Found [IP: 91.189.92.200 80]
Ign http://archive.ubuntu.com maverick-backports/main Translation-en_US
Ign http://archive.ubuntu.com maverick-backports/main Translation-en
Ign http://archive.ubuntu.com maverick-backports/multiverse Translation-en_US
Ign http://archive.ubuntu.com maverick-backports/multiverse Translation-en
Ign http://archive.ubuntu.com maverick-backports/restricted Translation-en_US
Ign http://archive.ubuntu.com maverick-backports/restricted Translation-en
Ign http://archive.ubuntu.com maverick-backports/universe Translation-en_US
Ign http://archive.ubuntu.com maverick-backports/universe Translation-en
Get:15 http://security.ubuntu.com oneiric-security/multiverse i386 Packages [3,386 B]
Get:16 http://security.ubuntu.com oneiric-security/universe i386 Packages [65.3 kB]
Get:17 http://ubuntu.sth.sze.hu oneiric-updates/restricted i386 Packages [6,645 B]
Get:18 http://ubuntu.sth.sze.hu oneiric-updates/universe i386 Packages [146 kB]
Get:19 http://security.ubuntu.com oneiric-security/main TranslationIndex [74 B]
Get:20 http://security.ubuntu.com oneiric-security/multiverse TranslationIndex [72 B]
Get:21 http://security.ubuntu.com oneiric-security/restricted TranslationIndex [71 B]
Get:22 http://security.ubuntu.com oneiric-security/universe TranslationIndex [73 B]
Get:23 http://security.ubuntu.com oneiric-security/main Translation-en [112 kB]
Get:24 http://ubuntu.sth.sze.hu oneiric-updates/multiverse i386 Packages [6,371 B]
Get:25 http://ubuntu.sth.sze.hu oneiric-updates/main TranslationIndex [74 B]
Get:26 http://ubuntu.sth.sze.hu oneiric-updates/multiverse TranslationIndex [72 B]
Get:27 http://ubuntu.sth.sze.hu oneiric-updates/restricted TranslationIndex [72 B]
Get:28 http://ubuntu.sth.sze.hu oneiric-updates/universe TranslationIndex [73 B]
Hit http://ubuntu.sth.sze.hu oneiric-backports/main Sources
Hit http://ubuntu.sth.sze.hu oneiric-backports/restricted Sources
Hit http://ubuntu.sth.sze.hu oneiric-backports/universe Sources
Hit http://ubuntu.sth.sze.hu oneiric-backports/multiverse Sources
Hit http://ubuntu.sth.sze.hu oneiric-backports/main i386 Packages
Hit http://ubuntu.sth.sze.hu oneiric-backports/restricted i386 Packages
Hit http://ubuntu.sth.sze.hu oneiric-backports/universe i386 Packages
Hit http://ubuntu.sth.sze.hu oneiric-backports/multiverse i386 Packages
Hit http://ubuntu.sth.sze.hu oneiric-backports/main TranslationIndex
Hit http://ubuntu.sth.sze.hu oneiric-backports/multiverse TranslationIndex
Hit http://ubuntu.sth.sze.hu oneiric-backports/restricted TranslationIndex
Hit http://ubuntu.sth.sze.hu oneiric-backports/universe TranslationIndex
Get:29 http://ubuntu.sth.sze.hu oneiric-security/main Sources [66.4 kB]
Hit http://security.ubuntu.com oneiric-security/multiverse Translation-en
Hit http://security.ubuntu.com oneiric-security/restricted Translation-en
Get:30 http://ubuntu.sth.sze.hu oneiric-security/restricted Sources [1,964 B]
Get:31 http://ubuntu.sth.sze.hu oneiric-security/universe Sources [26.7 kB]
Get:32 http://ubuntu.sth.sze.hu oneiric-security/multiverse Sources [1,684 B]
Get:33 http://ubuntu.sth.sze.hu oneiric-security/main i386 Packages [239 kB]
Hit http://security.ubuntu.com oneiric-security/universe Translation-en
Get:34 http://ubuntu.sth.sze.hu oneiric-security/restricted i386 Packages [4,062 B]
Get:35 http://ubuntu.sth.sze.hu oneiric-security/universe i386 Packages [65.3 kB]
Get:36 http://ubuntu.sth.sze.hu oneiric-security/multiverse i386 Packages [3,386 B]
Get:37 http://ubuntu.sth.sze.hu oneiric-security/main TranslationIndex [74 B]
Get:38 http://ubuntu.sth.sze.hu oneiric-security/multiverse TranslationIndex [72 B]
Get:39 http://ubuntu.sth.sze.hu oneiric-security/restricted TranslationIndex [71 B]
Get:40 http://ubuntu.sth.sze.hu oneiric-security/universe TranslationIndex [73 B]
Hit http://ubuntu.sth.sze.hu oneiric/main Translation-en
Hit http://ubuntu.sth.sze.hu oneiric/multiverse Translation-en
Hit http://ubuntu.sth.sze.hu oneiric/restricted Translation-en
Hit http://ubuntu.sth.sze.hu oneiric/universe Translation-en
Get:41 http://ubuntu.sth.sze.hu oneiric-updates/main Translation-en [206 kB]
Hit http://ubuntu.sth.sze.hu oneiric-updates/multiverse Translation-en
Hit http://ubuntu.sth.sze.hu oneiric-updates/restricted Translation-en
Hit http://ubuntu.sth.sze.hu oneiric-updates/universe Translation-en
Hit http://ubuntu.sth.sze.hu oneiric-backports/main Translation-en
Hit http://ubuntu.sth.sze.hu oneiric-backports/multiverse Translation-en
Hit http://ubuntu.sth.sze.hu oneiric-backports/restricted Translation-en
Hit http://ubuntu.sth.sze.hu oneiric-backports/universe Translation-en
Get:42 http://ubuntu.sth.sze.hu oneiric-security/main Translation-en [112 kB]
Hit http://ubuntu.sth.sze.hu oneiric-security/multiverse Translation-en
Hit http://ubuntu.sth.sze.hu oneiric-security/restricted Translation-en
Hit http://ubuntu.sth.sze.hu oneiric-security/universe Translation-en
Ign http://packages.medibuntu.org oneiric/free Translation-en_US
Ign http://packages.medibuntu.org oneiric/free Translation-en
Ign http://packages.medibuntu.org oneiric/non-free Translation-en_US
Ign http://packages.medibuntu.org oneiric/non-free Translation-en
Fetched 2,110 kB in 6s (348 kB/s)
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/maverick-backports/main/binary-i386/Packages 404 Not Found [IP: 91.189.92.200 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/maverick-backports/restricted/binary-i386/Packages 404 Not Found [IP: 91.189.92.200 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/maverick-backports/universe/binary-i386/Packages 404 Not Found [IP: 91.189.92.200 80]

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/maverick-backports/multiverse/binary-i386/Packages 404 Not Found [IP: 91.189.92.200 80]

E: Some index files failed to download. They have been ignored, or old ones used instead.

To NikTh:

Thank you for your reply.
I am sorry I didn't specify that I had a kind of solution in mind that didn't involve backing up everything and doing a clean install.
That remains to be the final option, of course.

Cheers,
Han Shan

What is the output of:

lsb_release -a; uname -a

Thanks

It says that no lsb modules are available

ok, what is the output of:

cat /etc/issue

Thanks

This is what I got:

Ubuntu 11.10 \n \l

Disable the backports repo. Can help

Tried it. No luck. Thanks anyway.

Anyone else with a possible solution?

Before you can do a version upgrade, you have to make sure that you current release is up-to-date and that your package management system is clean.

The output of the apt-get update command shows that you have a wrong setting in the list of repositories. In addition to the oneiric sources, you still have maverick-backports enabled, which does not fit together.

My advice:
disable maverick-backports from your sources
try the following commands

sudo apt-get update
sudo apt-get upgrade

If there is any warning or error, please follow steps 1 to 6 of https://help.ubuntu.com/community/PackageManagerTroubleshootingProcedure with the only exception that in step 6 you should not create a new question, but should continue in this current question document.