Can't install 'ubuntu-desktop'

[Simon]

This happens when I try to update my 14.04 installation

This is the error message window

"It was impossible to install a required package. Please report this as a bug using 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal."

So this is what I did to get here

---------------------------------------------
as per instructions below

1)Description: Ubuntu 14.04.2 LTS
Release: 14.04
2) N: Unable to locate package pkgname
3) install updates
4) Asked to report this

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.7
ProcVersionSignature: Ubuntu 3.13.0-43.72-generic 3.13.11.11
Uname: Linux 3.13.0-43-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.10
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Tue Jun 2 07:09:23 2015
InstallationDate: Installed on 2014-07-09 (327 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

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