"Could not calculate the upgrade" error when trying to upgrade from Natty to Oneiric

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Error box states:
------------
An unresolvable problem occurred while calculating the upgrade:
E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.

 This can be caused by:
 * Upgrading to a pre-release version of Ubuntu
 * Running the current pre-release version of Ubuntu
 * Unofficial software packages not provided by Ubuntu
--------------
however, none of the bulleted issues apply.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: update-manager 1:0.150.5
ProcVersionSignature: Ubuntu 2.6.38-13.52-generic 2.6.38.8
Uname: Linux 2.6.38-13-generic x86_64
NonfreeKernelModules: nvidia
Architecture: amd64
Date: Wed Nov 23 19:31:22 2011
GConfNonDefault:
 /apps/update-manager/check_new_release_ignore=
 /apps/update-manager/first_run=false
 /apps/update-manager/window_size=(600,600)
InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release amd64 (20100816.1)
PackageArchitecture: all
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
UpgradeStatus: Upgraded to natty on 2011-11-24 (0 days ago)
VarLogDistupgradeApttermlog:

VarLogDistupgradeHistorylog:

VarLogDistupgradeTermlog:

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[dino99 (9d9)]

That version is no more maintained