maximized windows sometimes change monitor when changing virtual desktop

In normal usage, I have 2 monitors (LCD on laptop and external display).
I bounce back and forth between virtual desktops fairly regularly using keyboard shortcuts .

Occasionally, when changing virtual desktops, a window that was maximized on the LCD will pop over to the external display.

I've seen this at least through raring cycle and still in saucy. I'm not sure what triggers it, but when it happens I have to drag the window back to the right screen.

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: unity 7.0.0daily13.04.18~13.04-0ubuntu1
ProcVersionSignature: Ubuntu 3.8.0-21.32-generic 3.8.8
Uname: Linux 3.8.0-21-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.10.2-0ubuntu1
Architecture: amd64
CompizPlugins: [core,bailer,detection,composite,opengl,compiztoolbox,decor,snap,commands,mousepoll,grid,move,place,imgpng,session,vpswitch,resize,regex,gnomecompat,unitymtgrabhandles,wall,resizeinfo,animation,workarounds,fade,scale,expo,ezoom,unityshell]
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
Date: Thu May 30 08:42:22 2013
DistUpgraded: 2013-05-20 08:14:41,880 DEBUG openCache()
DistroCodename: saucy
DistroVariant: ubuntu
EcryptfsInUse: Yes
GraphicsCard:
 Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller [8086:2a42] (rev 07) (prog-if 00 [VGA controller])
   Subsystem: Lenovo Device [17aa:20e4]
   Subsystem: Lenovo Device [17aa:20e4]
InstallationDate: Installed on 2011-10-19 (588 days ago)
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
MachineType: LENOVO 7417CTO
MarkForUpload: True
PccardctlIdent:
 Socket 0:
   no product info available
PccardctlStatus:
 Socket 0:
   no card
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-21-generic root=UUID=f9832678-e9fb-41c5-8edb-5edd5200ed0a ro quiet splash vt.handoff=7
SourcePackage: unity
UpgradeStatus: Upgraded to saucy on 2013-05-20 (10 days ago)
dmi.bios.date: 12/06/2010
dmi.bios.vendor: LENOVO
dmi.bios.version: 7UET91WW (3.21 )
dmi.board.name: 7417CTO
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr7UET91WW(3.21):bd12/06/2010:svnLENOVO:pn7417CTO:pvrThinkPadT400:rvnLENOVO:rn7417CTO:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 7417CTO
dmi.product.version: ThinkPad T400
dmi.sys.vendor: LENOVO
version.compiz: compiz 1:0.9.9~daily13.04.18.1~13.04-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.45-1
version.libgl1-mesa-dri: libgl1-mesa-dri 9.1.3-0ubuntu1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 9.1.3-0ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.13.3-0ubuntu10
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.7.3-0ubuntu2b2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.1.0-0ubuntu2
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.21.6-0ubuntu4
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.7-0ubuntu1
xserver.bootTime: Wed May 22 12:25:28 2013
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.version: 2:1.13.3-0ubuntu9
xserver.video_driver: intel