Compiz broken installation this morning - removed packages

[James Clemence]

Having run apt-get update, apt-get upgrade this morning, part of the package process removed unity and compiz from the system, I think due to broken dependencies:

The following packages have unmet dependencies.
 unity : Depends: compiz but it is not going to be installed
         Depends: compiz-core-abiversion-20120216 but it is not installable
         Depends: libnux-abiversion-20120212.01 but it is not installable
         Depends: compiz-plugins-main-default but it is not going to be installed
         Recommends: unity-lens-video but it is not going to be installed
         Recommends: indicator-printers but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Clearly this shouldn't happen (removing the core GUI elements from the system). Could this be resolved?

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: compiz (not installed)
ProcVersionSignature: Ubuntu 3.2.0-18.29-generic 3.2.9
Uname: Linux 3.2.0-18-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 1.94.1-0ubuntu2
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
Date: Mon Mar 12 13:21:29 2012
DistUpgraded: Log time: 2012-03-10 18:41:09.396871
DistroCodename: precise
DistroVariant: ubuntu
DkmsStatus:
 virtualbox, 4.1.8, 3.0.0-16-generic, x86_64: installed
 virtualbox, 4.1.8, 3.2.0-18-generic, x86_64: installed
 wacom, 0.12.1, 3.0.0-16-generic, x86_64: installed
 wacom, 0.12.1, 3.2.0-18-generic, x86_64: installed
EcryptfsInUse: Yes
GraphicsCard:
 Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller [8086:0116] (rev 09) (prog-if 00 [VGA controller])
   Subsystem: Dell Device [1028:0510]
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Beta amd64 (20110920.5)
MachineType: Dell Inc. Vostro V131
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/usr/bin/zsh
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-18-generic root=UUID=405eef45-c45e-4c66-8de8-a247789197bf ro quiet splash vt.handoff=7
SourcePackage: compiz
UpgradeStatus: Upgraded to precise on 2012-03-10 (1 days ago)
dmi.bios.date: 08/31/2011
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A02
dmi.board.name: 0W2GXJ
dmi.board.vendor: Dell Inc.
dmi.board.version: A02
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: Not Specified
dmi.modalias: dmi:bvnDellInc.:bvrA02:bd08/31/2011:svnDellInc.:pnVostroV131:pvrNotSpecified:rvnDellInc.:rn0W2GXJ:rvrA02:cvnDellInc.:ct8:cvrNotSpecified:
dmi.product.name: Vostro V131
dmi.product.version: Not Specified
dmi.sys.vendor: Dell Inc.
version.compiz: compiz N/A
version.ia32-libs: ia32-libs 20090808ubuntu33
version.libdrm2: libdrm2 2.4.30-1ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 8.0.1-0ubuntu2
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 8.0.1-0ubuntu2
version.xserver-xorg-core: xserver-xorg-core 2:1.11.4-0ubuntu6
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.6.99.901+git20120126-0ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.14.99~git20111219.aacbd629-0ubuntu2
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.17.0-1ubuntu4
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:0.0.16+git20111201+b5534a1-1build2