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Since upgrading Ubuntu yesterday, I've seen several instances where my session has crashed and forced me back to the login screen. A quick peek at the Xorg logs shows a segmentation fault with the following information logged:

[ 12554.427] 
[ 12554.427] 0: /usr/bin/X (xorg_backtrace+0x3b) [0x80eab1b]
[ 12554.427] 1: /usr/bin/X (0x8048000+0x5fac8) [0x80a7ac8]
[ 12554.427] 2: (vdso) (__kernel_rt_sigreturn+0x0) [0xb780d40c]
[ 12554.427] 3: /usr/bin/X (_CallCallbacks+0x3e) [0x8074e1e]
[ 12554.427] 4: /usr/bin/X (WriteToClient+0x267) [0x80a7607]
[ 12554.428] 5: /usr/lib/xorg/modules/extensions/ (ProcDRI2WaitMSCReply+0x62) [0xb73c2bf2]
[ 12554.428] 6: /usr/lib/xorg/modules/extensions/ (DRI2WaitMSCComplete+0x75) [0xb73c0fc5]
[ 12554.428] 7: /usr/lib/xorg/modules/drivers/ (0xb7357000+0x226bc) [0xb73796bc]
[ 12554.428] 8: /usr/lib/xorg/modules/drivers/ (0xb7357000+0x87d2) [0xb735f7d2]
[ 12554.428] 9: /lib/i386-linux-gnu/ (drmHandleEvent+0xf5) [0xb73a8665]
[ 12554.428] 10: /usr/lib/xorg/modules/drivers/ (0xb7357000+0x7937) [0xb735e937]
[ 12554.428] 11: /usr/bin/X (WakeupHandler+0x52) [0x8074602]
[ 12554.428] 12: /usr/bin/X (WaitForSomething+0x1ba) [0x80a1f3a]
[ 12554.428] 13: /usr/bin/X (0x8048000+0x27f1e) [0x806ff1e]
[ 12554.428] 14: /usr/bin/X (0x8048000+0x1a81c) [0x806281c]
[ 12554.428] 15: /lib/i386-linux-gnu/ (__libc_start_main+0xe7) [0xb7520e37]
[ 12554.428] 16: /usr/bin/X (0x8048000+0x1a411) [0x8062411]
[ 12554.428] Segmentation fault at address 0xb347e008
[ 12554.428] 
Caught signal 11 (Segmentation fault). Server aborting
[ 12554.428] 
Please consult the The X.Org Foundation support 
 for help. 
[ 12554.428] Please also check the log file at "/var/log/Xorg.0.log" for additional information.
[ 12554.428] 

I've not seen anything recent on any of the mailing lists that seems to resemble this problem, and I'm wondering whether anyone else has encountered a similar issue and whether or not there's a fix for it. Any help would be appreciated.

HP Compaq 6730b (GB991EA#AKB) (GB991EA#AKB)
Intel(R) Core(TM)2 Duo CPU     T9400  @ 2.53GHz

ck1@cantor:/var/log$ uname -mrs
Linux 2.6.38-8-generic-pae i686
ck1@cantor:/var/log$ lsb_release -a
Distributor ID: Ubuntu
Description:    Ubuntu 11.04
Release:    11.04
Codename:   natty

  description: VGA compatible controller
  product: Mobile 4 Series Chipset Integrated Graphics Controller
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After paging through lots of similar bugs on Ubuntu Launchpad, I found one suggestion that went along with my theory that the default Compiz effects settings were too advanced for my hardware setup.

compiz efects disables:
-Enchanced Zoom Desktop
-Snapping Windows

I've been back using Unity for about 24 hours with no crashes so far, so I'm accepting that this is at least a reasonably stable workaround.

See the original posting at:

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