Firefox crashes very frequently if flash plugin is enabled

[Brain]

If flash-plugin is installed (does not matter if adobe-flashplugin package or flashplugin-installer or using flash-aid) and enabled then firefox crashes unexpectedly and very frequently on pages using flash (adverts, videos, etc.) It's almost impossible to browse the internet. This bug is very annoying.

The problem popped up after I upgraded to Ubuntu 12.04. In the previous version 10.10 the flash was crashing as well, but not that often.

Firefox version:
firefox:
  Installed: 12.0+build1-0ubuntu0.12.04.1
  Candidate: 12.0+build1-0ubuntu0.12.04.1
  Version table:
 *** 12.0+build1-0ubuntu0.12.04.1 0
        500 http://ch.archive.ubuntu.com/ubuntu/ precise-updates/main i386 Packages
        500 http://security.ubuntu.com/ubuntu/ precise-security/main i386 Packages
        100 /var/lib/dpkg/status
     11.0+build1-0ubuntu4 0
        500 http://ch.archive.ubuntu.com/ubuntu/ precise/main i386 Packages

The problem seems to be caused by "X_CopyArea: BadMatch" in the flash plugin. See more information from Mozilla debugger:

Add-ons: {d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d}:2.0.3,{c45c406e-ab73-11d8-be73-000a95be3b12}:1.1.9,{f13b157f-b174-47e7-a34d-4815ddfdfeb8}:0.9.89,php_dev_bar@php_dev_bar.org:3.0.5,<email address hidden>:12.0,<email address hidden>:12.0,<email address hidden>:3.2.3,<email address hidden>:2.0.3,<email address hidden>:2.2.3,{972ce4c6-7e08-4474-a285-3208198ce6fd}:12.0
BuildID: 20120423122624
CrashTime: 1337199379
EMCheckCompatibility: true
FramePoisonBase: 00000000f0dea000
FramePoisonSize: 4096
InstallTime: 1336813451
Notes: OpenGL: Tungsten Graphics, Inc -- Mesa DRI Mobile Intel® GM45 Express Chipset x86/MMX/SSE2 -- 2.1 Mesa 8.0.2 -- texture_from_pixmap
X_CopyArea: BadMatch (invalid parameter attributes); 2 requests agoxpcom_runtime_abort(###!!! ABORT: X_CopyArea: BadMatch (invalid parameter attributes); 2 requests ago: file /build/buildd/firefox-12.0+build1/build-tree/mozilla/toolkit/xre/nsX11ErrorHandler.cpp, line 190)
ProductID: {ec8030f7-c20a-464f-9b0e-13a3a9e97384}
ProductName: Firefox
ReleaseChannel: release
SecondsSinceLastCrash: 2629
StartupTime: 1337199342
Theme: classic/1.0
Throttleable: 1
URL: http://www.topgear.com/au/videos/
Vendor: Mozilla
Version: 12.0

This report also contains technical information about the state of the application when it crashed.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: firefox 12.0+build1-0ubuntu0.12.04.1
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic-pae 3.2.14
Uname: Linux 3.2.0-24-generic-pae i686
AddonCompatCheckDisabled: False
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 2.0.1-0ubuntu7
Architecture: i386
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: STAC92xx Analog [STAC92xx Analog]
   Subdevices: 2/2
   Subdevice #0: subdevice #0
   Subdevice #1: subdevice #1
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: brain 1988 F.... pulseaudio
BuildID: 20120423122624
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xf6afc000 irq 47'
   Mixer name : 'IDT 92HD71B7X'
   Components : 'HDA:111d76b2,102802aa,00100302'
   Controls : 27
   Simple ctrls : 16
Channel: release
Date: Wed May 16 22:31:05 2012
EcryptfsInUse: Yes
ForcedLayersAccel: False
IfupdownConfig:
 auto lo
 iface lo inet loopback
InstallationMedia: Kubuntu 9.10 "Karmic Koala" - Release i386 (20091028.5)
IpRoute:
 default via 192.168.2.1 dev eth0 proto static
 192.168.2.0/24 dev eth0 proto kernel scope link src 192.168.2.105 metric 1
ProcEnviron:
 SHELL=/bin/bash
 PATH=(custom, user)
 LANG=en_US.UTF-8
 LANGUAGE=en_US:en
Profiles: Profile0 (Default) - LastVersion=12.0/20120423122624 (Running)
RunningIncompatibleAddons: False
SourcePackage: firefox
UpgradeStatus: Upgraded to precise on 2012-05-12 (4 days ago)
dmi.bios.date: 12/07/2009
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A14
dmi.board.name: 0G848F
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA14:bd12/07/2009:svnDellInc.:pnInspiron1545:pvr:rvnDellInc.:rn0G848F:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: Inspiron 1545
dmi.sys.vendor: Dell Inc.

[Chris Coulson (chrisccoulson)]

That's because you set dom.ipc.plugins.enabled.libflashplayer.so to false in about:config

[Wacław Jacek (waclawjacek)]

Confirming this bug. Indeed setting it to "true" (in my case it was "dom.ipc.plugins.enabled" that was set to false) helps, but I had to set it to "false" to prevent Firefox from working really slowly when there was a Flash video when I was using GNU IceCat (a rebrand of Firefox) on Ubuntu 11.10.

[Wacław Jacek (waclawjacek)]

Uh, sorry. By "prevent Firefox" I mean "prevent the browser". Neither does Firefox, which I use now instead, work slowly nor crash with dom.ipc.plugins.enabled set to true on Ubuntu 12.04. :)