Xorg crashed with SIGABRT on nouveau in libexa

nothing special, just browsing Internet. And moving files from HDD to an external USB HDD

ProblemType: Crash
DistroRelease: Ubuntu 13.04
Package: xserver-xorg-core 2:1.13.3-0ubuntu4
Uname: Linux 3.9.0-030900rc5-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.9.2-0ubuntu5
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
CrashCounter: 1
Date: Thu Apr 4 23:24:32 2013
DistUpgraded: 2013-01-13 21:46:37,516 DEBUG enabling apt cron job
DistroCodename: raring
DistroVariant: ubuntu
ExecutablePath: /usr/bin/Xorg
ExtraDebuggingInterest: Yes, if not too technical
GraphicsCard:
 NVIDIA Corporation GT216 [GeForce GT 220] [10de:0a20] (rev a2) (prog-if 00 [VGA controller])
   Subsystem: Micro-Star International Co., Ltd. Device [1462:2020]
InstallationDate: Installed on 2012-02-27 (401 days ago)
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
MachineType: MEDIONPC MS-7616
MarkForUpload: True
ProcCmdline: /usr/bin/X :0 -core -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
ProcEnviron:

ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.9.0-030900rc5-generic root=UUID=cded073e-f845-4947-970b-f8a4290c4c2b ro crashkernel=384M-2G:64M,2G-:128M quiet splash vt.handoff=7
Signal: 6
SourcePackage: xorg-server
StacktraceTop:
 ?? () 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
 ?? () from /usr/lib/xorg/modules/libexa.so
Title: Xorg crashed with SIGABRT
UpgradeStatus: Upgraded to raring on 2013-01-13 (81 days ago)
UserGroups:

dmi.bios.date: 01/13/2010
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: A7616MLN.20F
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: MS-7616
dmi.board.vendor: MEDIONPC
dmi.board.version: 1.0
dmi.chassis.type: 3
dmi.chassis.vendor: MEDIONPC
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrA7616MLN.20F:bd01/13/2010:svnMEDIONPC:pnMS-7616:pvr1.0:rvnMEDIONPC:rnMS-7616:rvr1.0:cvnMEDIONPC:ct3:cvr:
dmi.product.name: MS-7616
dmi.product.version: 1.0
dmi.sys.vendor: MEDIONPC
version.compiz: compiz 1:0.9.9~daily13.03.29-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.43-0ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 9.0.3-0ubuntu1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 9.0.3-0ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.13.3-0ubuntu4
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.7.3-0ubuntu2b2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.1.0-0ubuntu2
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.21.5-0ubuntu1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.7-0ubuntu1
xserver.bootTime: Fri Apr 5 00:01:48 2013
xserver.configfile: default
xserver.devices:
 input Power Button KEYBOARD, id 6
 input Power Button KEYBOARD, id 7
 input USB 2.0 PC Camera KEYBOARD, id 8
 input AT Translated Set 2 keyboard KEYBOARD, id 9
 input ImPS/2 Generic Wheel Mouse MOUSE, id 10
xserver.errors:
 Failed to load module "nvidia" (module does not exist, 0)
 Failed to load module "nvidia" (module does not exist, 0)
xserver.logfile: /var/log/Xorg.0.log
xserver.version: 2:1.13.3-0ubuntu4
xserver.video_driver: nouveau