update manager does not appear with upgrade button to install 12.04LTS

Can you give the output of:

sudo apt-get update; lsb_release -a

Thanks

I have the same problem. After tempering with few options in the "Settings..." here it is:

webdev@webdev-M50Vc:~$ sudo apt-get update; lsb_release -a
Ign http://extras.ubuntu.com oneiric InRelease
Ign http://archive.canonical.com oneiric InRelease
Hit http://extras.ubuntu.com oneiric Release.gpg
Hit http://archive.canonical.com oneiric Release.gpg
Ign http://archive.ubuntu.com oneiric InRelease
Ign http://archive.ubuntu.com oneiric-updates InRelease
Ign http://archive.ubuntu.com oneiric-security InRelease
Ign http://archive.ubuntu.com oneiric-backports InRelease
Hit http://extras.ubuntu.com oneiric Release
Hit http://archive.canonical.com oneiric Release
Get:1 http://packages.medibuntu.org oneiric InRelease [7,096 B]
Get:2 http://archive.ubuntu.com oneiric Release.gpg [198 B]
Hit http://extras.ubuntu.com oneiric/main Sources
Get:3 http://archive.ubuntu.com oneiric-updates Release.gpg [198 B]
Get:4 http://archive.ubuntu.com oneiric-security Release.gpg [198 B]
Hit http://archive.canonical.com oneiric/partner Sources
Hit http://extras.ubuntu.com oneiric/main i386 Packages
Ign http://extras.ubuntu.com oneiric/main TranslationIndex
Hit http://archive.canonical.com oneiric/partner i386 Packages
Ign http://archive.canonical.com oneiric/partner TranslationIndex
Get:5 http://archive.ubuntu.com oneiric-backports Release.gpg [198 B]
Get:6 http://archive.ubuntu.com oneiric Release [40.8 kB]
Get:7 http://packages.medibuntu.org oneiric/free i386 Packages [3,222 B]
Get:8 http://archive.ubuntu.com oneiric-updates Release [40.8 kB]
Get:9 http://archive.ubuntu.com oneiric-security Release [40.8 kB]
Get:10 http://archive.ubuntu.com oneiric-backports Release [40.8 kB]
Get:11 http://archive.ubuntu.com oneiric/main i386 Packages [1,226 kB]
Get:12 http://packages.medibuntu.org oneiric/non-free i386 Packages [6,418 B]
Ign http://extras.ubuntu.com oneiric/main Translation-en_US
Ign http://archive.canonical.com oneiric/partner Translation-en_US
Ign http://archive.canonical.com oneiric/partner Translation-en
Ign http://extras.ubuntu.com oneiric/main Translation-en
Ign http://packages.medibuntu.org oneiric/free TranslationIndex
Ign http://packages.medibuntu.org oneiric/non-free TranslationIndex
Get:13 http://archive.ubuntu.com oneiric/restricted i386 Packages [8,216 B]
Get:14 http://archive.ubuntu.com oneiric/universe i386 Packages [4,468 kB]
Get:15 http://archive.ubuntu.com oneiric/multiverse i386 Packages [119 kB]
Hit http://archive.ubuntu.com oneiric/main TranslationIndex
Hit http://archive.ubuntu.com oneiric/multiverse TranslationIndex
Hit http://archive.ubuntu.com oneiric/restricted TranslationIndex
Hit http://archive.ubuntu.com oneiric/universe TranslationIndex
Get:16 http://archive.ubuntu.com oneiric-updates/main i386 Packages [335 kB]
Get:17 http://archive.ubuntu.com oneiric-updates/restricted i386 Packages [6,631 B]
Get:18 http://archive.ubuntu.com oneiric-updates/universe i386 Packages [112 kB]
Get:19 http://archive.ubuntu.com oneiric-updates/multiverse i386 Packages [6,366 B]
Hit http://archive.ubuntu.com oneiric-updates/main TranslationIndex
Hit http://archive.ubuntu.com oneiric-updates/multiverse TranslationIndex
Hit http://archive.ubuntu.com oneiric-updates/restricted TranslationIndex
Hit http://archive.ubuntu.com oneiric-updates/universe TranslationIndex
Get:20 http://archive.ubuntu.com oneiric-security/main i386 Packages [111 kB]
Get:21 http://archive.ubuntu.com oneiric-security/restricted i386 Packages [3,939 B]
Get:22 http://archive.ubuntu.com oneiric-security/universe i386 Packages [34.8 kB]
Get:23 http://archive.ubuntu.com oneiric-security/multiverse i386 Packages [3,379 B]
Hit http://archive.ubuntu.com oneiric-security/main TranslationIndex
Hit http://archive.ubuntu.com oneiric-security/multiverse TranslationIndex
Hit http://archive.ubuntu.com oneiric-security/restricted TranslationIndex
Hit http://archive.ubuntu.com oneiric-security/universe TranslationIndex
Get:24 http://archive.ubuntu.com oneiric-backports/restricted i386 Packages [14 B]
Get:25 http://archive.ubuntu.com oneiric-backports/main i386 Packages [3,296 B]
Get:26 http://archive.ubuntu.com oneiric-backports/multiverse i386 Packages [14 B]
Get:27 http://archive.ubuntu.com oneiric-backports/universe i386 Packages [13.4 kB]
Hit http://archive.ubuntu.com oneiric-backports/main TranslationIndex
Hit http://archive.ubuntu.com oneiric-backports/multiverse TranslationIndex
Hit http://archive.ubuntu.com oneiric-backports/restricted TranslationIndex
Hit http://archive.ubuntu.com oneiric-backports/universe TranslationIndex
Hit http://archive.ubuntu.com oneiric/main Translation-en
Hit http://archive.ubuntu.com oneiric/multiverse Translation-en
Ign http://packages.medibuntu.org oneiric/free Translation-en_US
Hit http://archive.ubuntu.com oneiric/restricted Translation-en
Hit http://archive.ubuntu.com oneiric/universe Translation-en
Hit http://archive.ubuntu.com oneiric-updates/main Translation-en
Hit http://archive.ubuntu.com oneiric-updates/multiverse Translation-en
Hit http://archive.ubuntu.com oneiric-updates/restricted Translation-en
Hit http://archive.ubuntu.com oneiric-updates/universe Translation-en
Hit http://archive.ubuntu.com oneiric-security/main Translation-en
Hit http://archive.ubuntu.com oneiric-security/multiverse Translation-en
Hit http://archive.ubuntu.com oneiric-security/restricted Translation-en
Hit http://archive.ubuntu.com oneiric-security/universe Translation-en
Hit http://archive.ubuntu.com oneiric-backports/main Translation-en
Hit http://archive.ubuntu.com oneiric-backports/multiverse Translation-en
Hit http://archive.ubuntu.com oneiric-backports/restricted Translation-en
Hit http://archive.ubuntu.com oneiric-backports/universe Translation-en
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 6,632 kB in 7s (932 kB/s)
Reading package lists... Done
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 11.10
Release: 11.10
Codename: oneiric
webdev@webdev-M50Vc:~$

ok and run:

sudo apt-get upgrade

Does it upgrade ok?

Negative...

webdev@webdev-M50Vc:~$ sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages have been kept back:
  xserver-xorg-video-openchrome
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
webdev@webdev-M50Vc:~$

Looks fine, is all ok now?

Nope, Andrew. Update-Manager still doesnt recognize any 12.04 nor asks me to upgrade.
All I get is this: http://i.imgur.com/yuNRX.png

Yes the package has been held back due to deps. This is ok