the browser fades just a little (greyness) and then everything freezes, the only feature that works is the x button to close the program. Sometimes the whole computer is affected also, and the m/c needs switching off. The problem is not found in safe mode

In safe mode all the add-ons are disabled, however i do not know how to disable single add-ons, in time before the system freezes, so it's either all on or all off.

 There shold be an additional feature to select which add-ons can be disabled before starting the browser. It must be one of these, since i prior to the problem when i had not so many, then i installed a number of them.

The browser is all still quite visible after the crash, though dull, and totoally lifeless/unresponsive, this usually happens about 1 minute after start up. and happens even if the machine is cold, or hot from no use or as yesterday when i enabled new add-ons -hot.

Other browsers were working fine.

I have noticed with regards the graphics on the computer this bug/error- or unkown: WebGL RendererBlocked for your graphics card because of unresolved driver issues.GPU Accelerated Windows Blocked for your graphics card because of unresolved driver issue

using ubuntu 12.04 LTS
Dell Compaq Dc7600 32 BIT
Intel® Pentium(R) 4 CPU 3.20GHz × 2
SOFTWARE CENTRE VERS ION 5.2.2
fIREFOX VERSION 12.0+build1-0ubuntu0.12.04.1

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: firefox 12.0+build1-0ubuntu0.12.04.1
ProcVersionSignature: Ubuntu 3.2.0-24.39-generic 3.2.16
Uname: Linux 3.2.0-24-generic i686
AddonCompatCheckDisabled: False
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
AplayDevices:
 **** List of PLAYBACK Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: ALC260 Analog [ALC260 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
ApportVersion: 2.0.1-0ubuntu7
Architecture: i386
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: ap 1993 F.... pulseaudio
BuildID: 20120423122624
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xe04c0000 irq 42'
   Mixer name : 'Realtek ALC260'
   Components : 'HDA:10ec0260,103c3010,00100400'
   Controls : 29
   Simple ctrls : 14
Channel: release
CurrentDmesg:
 [ 25.751380] tg3 0000:3f:00.0: eth0: Flow control is off for TX and off for RX
 [ 26.007782] linkstatus=DISCONNECTED (unhandled)
 [ 26.011222] ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
 [ 34.079663] init: plymouth-stop pre-start process (1613) terminated with status 1
 [ 36.880013] eth0: no IPv6 routers present
Date: Wed May 30 06:19:03 2012
ForcedLayersAccel: False
IfupdownConfig:
 auto lo
 iface lo inet loopback
IncompatibleExtensions:
 LastPass - <email address hidden>, Version=1.90.6, minVersion=1.9a2, maxVersion=1.9.6, Location=app-profile, Type=extension, Active=Yes
 Power Twitter - ID={b2509cd4-17cd-45ed-8146-a82af038f493}, Version=2.02, minVersion=1.5, maxVersion=9.*, Location=app-profile, Type=extension, Active=Yes
 SmoothWheel (AMO) - ID={5F590AA2-1221-4113-A6F4-A4BB62414FAC}, Version=0.45.6.20100202.1, minVersion=1.7, maxVersion=9.9.*, Location=app-profile, Type=extension, Active=Yes
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
IpRoute:
 default via 192.168.1.1 dev eth0 proto static
 169.254.0.0/16 dev eth0 scope link metric 1000
 192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.4 metric 1
Plugins:
 Shockwave Flash - Lib=libflashplayer.so, Location=/usr/lib/flashplugin-installer
 LibreOffice Plug-in - Lib=libnpsoplugin.so, Location=/usr/lib/libreoffice/program
 Gnome Shell Integration - Lib=libgnome-shell-browser-plugin.so, Location=/usr/lib/mozilla/plugins
 IcedTea-Web Plugin (using IcedTea-Web 1.2 (1.2-2ubuntu1)) - Lib=IcedTeaPlugin.so, Location=/usr/lib/jvm/java-6-openjdk-i386/jre/lib/i386
 iTunes Application Detector - Lib=librhythmbox-itms-detection-plugin.so, Location=/usr/lib/mozilla/plugins
ProcEnviron:
 LANGUAGE=en_GB:en
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
Profiles: Profile0 (Default) - LastVersion=12.0/20120423122624 (Running)
RfKill:
 0: phy0: Wireless LAN
  Soft blocked: no
  Hard blocked: no
RunningIncompatibleAddons: True
SourcePackage: firefox
UpgradeStatus: Upgraded to precise on 2012-05-08 (21 days ago)
dmi.bios.date: 07/01/2009
dmi.bios.vendor: Hewlett-Packard
dmi.bios.version: 786D1 v01.61
dmi.board.name: 09F0h
dmi.board.vendor: Hewlett-Packard
dmi.chassis.asset.tag: HUB5380GCN
dmi.chassis.type: 6
dmi.chassis.vendor: Hewlett-Packard
dmi.modalias: dmi:bvnHewlett-Packard:bvr786D1v01.61:bd07/01/2009:svnHewlett-Packard:pnHPCompaqdc7600ConvertibleMinitower:pvr:rvnHewlett-Packard:rn09F0h:rvr:cvnHewlett-Packard:ct6:cvr:
dmi.product.name: HP Compaq dc7600 Convertible Minitower
dmi.sys.vendor: Hewlett-Packard