Xorg crashed with SIGABRT

I had just installed Quantal Alpha 3 on a partition of my PC and launched apt-get upgrade and apt-get dist-upgrade and rebooted.
I was using firefox and crash occured.

I have this hardware: http://wiki.ubuntu-it.org/CarlaSella/lshw.

ProblemType: Crash
DistroRelease: Ubuntu 12.10
Package: xserver-xorg-core 2:1.12.99.904-0ubuntu2
ProcVersionSignature: Ubuntu 3.5.0-11.11-generic 3.5.2
Uname: Linux 3.5.0-11-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.4-0ubuntu9
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CrashCounter: 1
CurrentDmesg: [ 23.219493] init: plymouth-stop pre-start process (1286) terminated with status 1
Date: Wed Aug 22 13:52:38 2012
DistUpgraded: Fresh install
DistroCodename: quantal
DistroVariant: ubuntu
ExecutablePath: /usr/bin/Xorg
ExtraDebuggingInterest: Yes, even including gdb or git bisection work if needed
GraphicsCard:
 NVIDIA Corporation G86 [GeForce 8400 GS] [10de:0422] (rev a1) (prog-if 00 [VGA controller])
   Subsystem: XFX Pine Group Inc. Device [1682:2310]
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha amd64 (20120724.2)
MachineType: System manufacturer System Product Name
ProcCmdline: /usr/bin/X :0 -core -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
ProcEnviron:

ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.5.0-11-generic root=UUID=8e43d34d-2ebd-49ef-8587-4d71c99c9d41 ro quiet splash vt.handoff=7
Renderer: Software
Signal: 6
SourcePackage: xorg-server
StacktraceTop:
 ?? () from /lib/x86_64-linux-gnu/libc.so.6
 ?? () from /usr/lib/xorg/modules/libexa.so
 ?? () from /usr/lib/xorg/modules/libexa.so
 ?? () from /usr/lib/xorg/modules/libexa.so
 ?? () from /usr/lib/xorg/modules/libexa.so
Title: Xorg crashed with SIGABRT
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

dmi.bios.date: 05/28/2007
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 0702
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: M2N
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: Rev 1.xx
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr0702:bd05/28/2007:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnM2N:rvrRev1.xx:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.name: System Product Name
dmi.product.version: System Version
dmi.sys.vendor: System manufacturer
version.compiz: compiz 1:0.9.8+bzr3249-0ubuntu4
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.38-0ubuntu2
version.libgl1-mesa-dri: libgl1-mesa-dri 8.0.4-1ubuntu1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 8.0.4-1ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.12.99.904-0ubuntu2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.7.3-0ubuntu1
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.99.99~git20120713.6ef1ad6a-0ubuntu1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.20.3-0ubuntu1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.1-4~ubuntu1