Flash content raised above all other windows after hover

Go to https://github.com/chris-twiner/scalesXml and hover the mouse over the little clipboard icon to the right of the repository URL (on the line that starts "ZIP HTTP SSH"...)

The icon will now stay above all other windows if you switch to another window on that display. However, the problem somehow resolves itself after a short while, until the clipboard icon is hovered over again.

This is 100% reproducable. I think it only started happening recently - I've used this button before so I'm pretty sure I'd have noticed it if it had been happening before.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: firefox 17.0+build2-0ubuntu0.12.04.1
ProcVersionSignature: Ubuntu 3.2.0-34.53-generic-pae 3.2.33
Uname: Linux 3.2.0-34-generic-pae i686
NonfreeKernelModules: nvidia wl
AddonCompatCheckDisabled: False
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 2.0.1-0ubuntu15
Architecture: i386
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: PCH [HDA Intel PCH], device 0: STAC92xx Analog [STAC92xx Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: robin 2348 F.... pulseaudio
 /dev/snd/controlC0: robin 2348 F.... pulseaudio
BuildID: 20121120042814
CRDA: Error: command ['iw', 'reg', 'get'] failed with exit code 1: nl80211 not found.
Card0.Amixer.info:
 Card hw:0 'PCH'/'HDA Intel PCH at 0xe6760000 irq 44'
   Mixer name : 'IDT 92HD90BXX'
   Components : 'HDA:111d76e7,10280494,00100102'
   Controls : 20
   Simple ctrls : 11
Card1.Amixer.info:
 Card hw:1 'NVidia'/'HDA NVidia at 0xe5080000 irq 17'
   Mixer name : 'Nvidia GPU 1c HDMI/DP'
   Components : 'HDA:10de001c,10280494,00100100'
   Controls : 18
   Simple ctrls : 3
Channel: Unavailable
Date: Tue Nov 27 10:58:34 2012
DefaultProfilePrefSources: prefs.js
EcryptfsInUse: Yes
ExecutablePath: /usr/lib/firefox/firefox
ForcedLayersAccel: False
IfupdownConfig:
 auto lo
 iface lo inet loopback
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
IpRoute:
 default via 10.252.50.1 dev eth0 proto static
 10.252.50.0/24 dev eth0 proto kernel scope link src 10.252.50.20 metric 1
 169.254.0.0/16 dev eth0 scope link metric 1000
LocalLibraries: /opt/google/talkplugin/libnpgtpo3dautoplugin.so /opt/google/talkplugin/lib/libCgGL.so /opt/google/talkplugin/lib/libCg.so /opt/google/talkplugin/libnpgoogletalk.so
MarkForUpload: True
MostRecentCrashID: bp-e12e7cf9-9e47-4913-a520-460452120511
ProcEnviron:
 LANGUAGE=en_GB:en
 PATH=(custom, user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
Profile1PrefSources: prefs.js
Profiles:
 Profile0 (Default) - LastVersion=17.0/20121120042814 (In use)
 Profile1 - LastVersion=17.0/20121120042814
RunningIncompatibleAddons: False
SourcePackage: firefox
UpgradeStatus: Upgraded to precise on 2012-04-27 (214 days ago)
WifiSyslog:

dmi.bios.date: 05/24/2011
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A05
dmi.board.name: 0J4TFW
dmi.board.vendor: Dell Inc.
dmi.board.version: A01
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA05:bd05/24/2011:svnDellInc.:pnLatitudeE6520:pvr01:rvnDellInc.:rn0J4TFW:rvrA01:cvnDellInc.:ct9:cvr:
dmi.product.name: Latitude E6520
dmi.product.version: 01
dmi.sys.vendor: Dell Inc.