unity panel won't display when windows are maxmised

The Unity panel on the RHS of the screen displayed as I would expect on empty desktops and when the desktop does not contain a maximized window - i.e. its automatically displayed.

However when I have a maximized window, I can't get the unity panel to display using the mouse.

I've tried this both on my day-to-day account and a fresh account (to make sure I did not have cranky settings).

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: unity 4.22.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-12.19-generic 3.0.4
Uname: Linux 3.0.0-12-generic x86_64
NonfreeKernelModules: fglrx
.tmp.unity.support.test.0:

ApportVersion: 1.23-0ubuntu2
Architecture: amd64
CompizPlugins: [core,bailer,detection,composite,opengl,compiztoolbox,decor,imgpng,grid,move,gnomecompat,snap,mousepoll,unitymtgrabhandles,resize,regex,vpswitch,place,session,wall,animation,expo,workarounds,fade,ezoom,scale,unityshell]
CompositorRunning: compiz
Date: Wed Oct 5 09:33:26 2011
DistUpgraded: Log time: 2011-09-09 16:10:05.632536
DistroCodename: oneiric
DistroVariant: ubuntu
DkmsStatus: fglrx, 8.881, 3.0.0-12-generic, x86_64: installed
GraphicsCard:
 ATI Technologies Inc Manhattan [Mobility Radeon HD 5400 Series] [1002:68e0] (prog-if 00 [VGA controller])
   Subsystem: Dell Device [1028:0413]
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110426)
JockeyStatus:
 xorg:fglrx_updates - ATI/AMD proprietary FGLRX graphics driver (post-release updates) (Proprietary, Disabled, Not in use)
 xorg:fglrx - ATI/AMD proprietary FGLRX graphics driver (Proprietary, Enabled, In use)
MachineType: Dell Inc. Studio 1558
PlymouthDebug: Error: [Errno 13] Permission denied: '/var/log/plymouth-debug.log'
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.0.0-12-generic root=/dev/mapper/hostname-root ro quiet splash plymouth:debug vt.handoff=7
SourcePackage: unity
UpgradeStatus: Upgraded to oneiric on 2011-09-09 (25 days ago)
dmi.bios.date: 06/24/2010
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A07
dmi.board.name: 0874P6
dmi.board.vendor: Dell Inc.
dmi.board.version: A07
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: A07
dmi.modalias: dmi:bvnDellInc.:bvrA07:bd06/24/2010:svnDellInc.:pnStudio1558:pvrA07:rvnDellInc.:rn0874P6:rvrA07:cvnDellInc.:ct8:cvrA07:
dmi.product.name: Studio 1558
dmi.product.version: A07
dmi.sys.vendor: Dell Inc.
version.compiz: compiz 1:0.9.6+bzr20110929-0ubuntu3
version.fglrx-installer: fglrx-installer N/A
version.ia32-libs: ia32-libs 20090808ubuntu25
version.libdrm2: libdrm2 2.4.26-1ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 7.11-0ubuntu3
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 7.11-0ubuntu3
version.xserver-xorg: xserver-xorg 1:7.6+7ubuntu7
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.6.0-1ubuntu13
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.14.99~git20110811.g93fc084-0ubuntu1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.15.901-1ubuntu2
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:0.0.16+git20110411+8378443-1