firefox window goes grey/gray whilst doing giant IO reads

[Alan Pope 🍺🐧🐱 🦄]

When I start firefox from cold it loads my tabs and all seems fine for a bit, then shortly after the window goes dark, it's unusable. I run iotop and discover firefox is reading about 1.2MB/s for about 5 minutes. I have to wait until this has finished, and can then continue to use it. The amount of IO seems to block everything else. For example just taking a screenshot worked, but then saving it took a long time (15 seconds) whilst the disk (SSD) was massively busy.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: firefox 13.0+build1-0ubuntu0.12.04.1
ProcVersionSignature: Ubuntu 3.2.0-26.41-generic 3.2.19
Uname: Linux 3.2.0-26-generic x86_64
AddonCompatCheckDisabled: False
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 2.0.1-0ubuntu9
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: PCH [HDA Intel PCH], device 0: CONEXANT Analog [CONEXANT Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: alan 2734 F.... pulseaudio
BuildID: 20120601175215
Card0.Amixer.info:
 Card hw:0 'PCH'/'HDA Intel PCH at 0xf2620000 irq 51'
   Mixer name : 'Intel CougarPoint HDMI'
   Components : 'HDA:14f1506e,17aa21da,00100002 HDA:80862805,80860101,00100000'
   Controls : 27
   Simple ctrls : 9
Card29.Amixer.info:
 Card hw:29 'ThinkPadEC'/'ThinkPad Console Audio Control at EC reg 0x30, fw unknown'
   Mixer name : 'ThinkPad EC (unknown)'
   Components : ''
   Controls : 1
   Simple ctrls : 1
Card29.Amixer.values:
 Simple mixer control 'Console',0
   Capabilities: pswitch pswitch-joined penum
   Playback channels: Mono
   Mono: Playback [on]
Channel: release
Date: Sat Jun 16 08:19:48 2012
EcryptfsInUse: Yes
ForcedLayersAccel: False
IfupdownConfig:
 auto lo
 iface lo inet loopback
IncompatibleExtensions: LastPass - <email address hidden>
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha amd64 (20120203)
IpRoute:
 default via 192.168.1.1 dev wlan0 proto static
 10.0.3.0/24 dev lxcbr0 proto kernel scope link src 10.0.3.1
 169.254.0.0/16 dev wlan0 scope link metric 1000
 192.168.1.0/24 dev wlan0 proto kernel scope link src 192.168.1.103 metric 2
 192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm
 PATH=(custom, user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
Profiles: Profile0 (Default) - LastVersion=13.0/20120601175215 (In use)
RelatedPackageVersions:
 rhythmbox-mozilla 2.97-0ubuntu1~webupd8~precise
 google-talkplugin 2.9.10.0-1
 totem-mozilla 3.0.1-0ubuntu21
RunningIncompatibleAddons: True
SourcePackage: firefox
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/15/2011
dmi.bios.vendor: LENOVO
dmi.bios.version: 8DET52WW (1.22 )
dmi.board.asset.tag: Not Available
dmi.board.name: 4287CTO
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:bvr8DET52WW(1.22):bd09/15/2011:svnLENOVO:pn4287CTO:pvrThinkPadX220:rvnLENOVO:rn4287CTO:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 4287CTO
dmi.product.version: ThinkPad X220
dmi.sys.vendor: LENOVO

[Launchpad Janitor (janitor)]

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