Can't install 'ubuntu-desktop'

[Christopher]

These popups appeared when trying to update:

Can't install 'ubuntu-desktop'

It was impossible to install a required package. Please report this as a bug using 'ubuntu-bug update-manager' in a terminal.

----

An unresolvable problem occurred while calculating the upgrade:
The package 'unity' is marked for removal but it is in the removal blacklist.

 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

This is most likely a transient problem. Please try again later.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: update-manager 1:0.156.7
ProcVersionSignature: Ubuntu 3.2.0-18.29-generic 3.2.9
Uname: Linux 3.2.0-18-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 1.94.1-0ubuntu2
Architecture: amd64
CurrentDmesg.txt:
 [ 68.387158] postgres (1646): /proc/1646/oom_adj is deprecated, please use /proc/1646/oom_score_adj instead.
 [ 69.600015] wlan0: no IPv6 routers present
 [ 79.508624] init: plymouth-stop pre-start process (2721) terminated with status 1
Date: Mon Mar 12 10:13:21 2012
GsettingsChanges:
 com.ubuntu.update-manager first-run false
 com.ubuntu.update-manager launch-time 1331561539
 com.ubuntu.update-manager show-details true
 com.ubuntu.update-manager window-height 714
 com.ubuntu.update-manager window-width 641
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Alpha amd64 (20110803.1)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_CA:en
 LANG=en_CA.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
UpgradeStatus: Upgraded to precise on 2012-03-12 (0 days ago)

[Launchpad Janitor (janitor)]

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