Xorg crashed with SIGABRT

this comes from an auto-generated bug report, the system itself seems pretty stable (xorg starts everytime)

ProblemType: Crash
DistroRelease: Ubuntu 14.04
Package: xserver-xorg-core 2:1.15.0-1ubuntu7
ProcVersionSignature: Ubuntu 3.13.0-19.39-generic 3.13.6
Uname: Linux 3.13.0-17-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.13.3-0ubuntu1
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: Mon Mar 17 08:39:08 2014
DistUpgraded: 2014-03-16 19:40:31,152 DEBUG enabling apt cron job
DistroCodename: trusty
DistroVariant: ubuntu
DkmsStatus:
 virtualbox, 4.3.6, 3.11.0-18-generic, x86_64: installed
 virtualbox, 4.3.6, 3.13.0-17-generic, x86_64: installed
 virtualbox, 4.3.6, 3.13.0-19-generic, x86_64: installed
ExecutablePath: /usr/bin/Xorg
ExtraDebuggingInterest: Yes, if not too technical
GraphicsCard:
 NVIDIA Corporation G98M [GeForce 9300M GS] [10de:06e9] (rev a1) (prog-if 00 [VGA controller])
   Subsystem: Lenovo Device [17aa:2107]
InstallationDate: Installed on 2014-02-02 (48 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
MachineType: LENOVO 2746A69
ProcCmdline: /usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
ProcEnviron:

ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-19-generic root=UUID=9f9ca082-8bca-4b19-826f-7c0c698903f2 ro persistent 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 trusty on 2014-03-16 (6 days ago)
UserGroups:

dmi.bios.date: 12/01/2010
dmi.bios.vendor: LENOVO
dmi.bios.version: 6AET64WW
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: 2746A69
dmi.board.vendor: LENOVO
dmi.board.version: LENOVO 6AET64WW
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: LENOVO 6AET64WW
dmi.modalias: dmi:bvnLENOVO:bvr6AET64WW:bd12/01/2010:svnLENOVO:pn2746A69:pvr:rvnLENOVO:rn2746A69:rvrLENOVO6AET64WW:cvnLENOVO:ct10:cvrLENOVO6AET64WW:
dmi.product.name: 2746A69
dmi.sys.vendor: LENOVO
version.compiz: compiz 1:0.9.11+14.04.20140320.1-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.52-1
version.libgl1-mesa-dri: libgl1-mesa-dri 10.1.0-1ubuntu1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 10.1.0-1ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.15.0-1ubuntu7
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.8.2-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.3.0-1ubuntu3
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.910-0ubuntu1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.10-1ubuntu2
xserver.bootTime: Sun Mar 23 17:41:56 2014
xserver.configfile: default
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: 2:1.15.0-1ubuntu7
xserver.video_driver: nouveau