Xorg crashed suddenly, black screen, had to re login

[Charles Ford]

Unknown cause, but xorg suddenly just crashed, causing a black screen and then the login screen showed again.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: xorg 1:7.7+1ubuntu4
Uname: Linux 3.9.0-030900rc5-generic i686
.tmp.unity.support.test.0:

ApportVersion: 2.9.2-0ubuntu5
Architecture: i386
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
Date: Wed Apr 10 16:01:19 2013
DistUpgraded: Fresh install
DistroCodename: raring
DistroVariant: ubuntu
DkmsStatus: virtualbox, 4.2.10, 3.8.0-16-generic, i686: installed
ExtraDebuggingInterest: Yes, if not too technical
GraphicsCard:
 Advanced Micro Devices [AMD] nee ATI RV370 [Mobility Radeon X300] [1002:5460] (prog-if 00 [VGA controller])
   Subsystem: Dell Device [1028:2002]
InstallationDate: Installed on 2013-04-06 (3 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Alpha i386 (20130402.1)
MachineType: Dell Inc. Inspiron 9300
MarkForUpload: True
PccardctlIdent:
 Socket 0:
   no product info available
PccardctlStatus:
 Socket 0:
   no card
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.9.0-030900rc5-generic root=/dev/mapper/ubuntu--vg-root ro quiet splash
SourcePackage: xorg
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 02/23/2005
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A02
dmi.board.name: 0C5668
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA02:bd02/23/2005:svnDellInc.:pnInspiron9300:pvr:rvnDellInc.:rn0C5668:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: Inspiron 9300
dmi.sys.vendor: Dell Inc.
version.compiz: compiz 1:0.9.9~daily13.04.05-0ubuntu1
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: Wed Apr 10 11:37:32 2013
xserver.configfile: default
xserver.errors:
 [mi] EQ overflowing. Additional events will be discarded until existing events are processed.

 Backtrace:

 Backtrace:
xserver.logfile: /var/log/Xorg.0.log
xserver.outputs: Output DVI-0 LVDS S-video VGA-0
xserver.version: 2:1.13.3-0ubuntu4
xserver.video_driver: radeon

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Sandis Krutovs (sandiskr)]

Same situation, only it happens so often, I cannot work properly anymore.

Description: I run or do something, then Xorg crashes showing me the black command line screen with booting information and then signup/login screen appears. All open GUI programms are closed, Xorg session is not saved. Most often, crash happens when I run something: skype, firefox, terminal, but it also happened when tried to open "find" window in Eclipse.

First, I suspected several different packages as causes, because they were running when all happens and they were complaining with crash reports. However, I was able to create situation, when those possible culprits were not running, Xorg crashed and no crash report was suggested at all.

I found no obvious (for me) errors in log files.

And I don't have ati video card (from lspci):
00:00.0 Host bridge: Intel Corporation Xeon E3-1200 v2/3rd Gen Core processor DRAM Controller (rev 09)
00:02.0 VGA compatible controller: Intel Corporation Xeon E3-1200 v2/3rd Gen Core processor Graphics Controller (rev 09)

Attaching Xorg log, that says "server terminated successfully" that happened on "crash".

[Sandis Krutovs (sandiskr)]

OS: Ubuntu 13.04, upgraded from 12.10