Comment 18 for bug 1174495

I don't know if its the same but i can confirm similar crashes.

First of all, i have a triple head setup, 2 screens with 1920x1200 (left and right) and one with 2560x1600 (middle). Those crashes happen since kernel 3.8 (i've used 3.8.[1-4]) and mesa-9.1 but i don't know which one actually introduced the problem as i both updated at the same time..
Furthermore they are no crashes at all if i disable desktop effects in kde.

Basically i only have to create an new user and login into it. Kde usually sets the resolution of all screens to 1920x1200 with enabled desktop effect. I can actually move the screens back and forth (because the ordering is wrong too with the first start) without problems, but as soon as i'm changing the resolution of the middle screen X crashes.
Without effects i won't get any crashes.

If you need more info, please let me know.

Below are the relevant parts of Xorg.0.log (even though without debug symbols i think its quite useless ;) ):

[ 1671.397] (EE)
[ 1671.397] (EE) Backtrace:
[ 1671.397] (EE) 0: /usr/bin/X (xorg_backtrace+0x36) [0x5860f6]
[ 1671.397] (EE) 1: /usr/bin/X (0x400000+0x189e09) [0x589e09]
[ 1671.397] (EE) 2: /lib64/libpthread.so.0 (0x7ff6d65e0000+0x10ff0) [0x7ff6d65f0ff0]
[ 1671.397] (EE) 3: /lib64/libc.so.6 (0x7ff6d5238000+0x8a6fb) [0x7ff6d52c26fb]
[ 1671.397] (EE) 4: /usr/lib64/dri/r600_dri.so (0x7ff6d2438000+0x5175c7) [0x7ff6d294f5c7]
[ 1671.397] (EE) 5: /usr/lib64/dri/r600_dri.so (0x7ff6d2438000+0x517a87) [0x7ff6d294fa87]
[ 1671.398] (EE) 6: /usr/lib64/dri/r600_dri.so (0x7ff6d2438000+0x52a0dd) [0x7ff6d29620dd]
[ 1671.398] (EE) 7: /usr/lib64/dri/r600_dri.so (0x7ff6d2438000+0x528c4d) [0x7ff6d2960c4d]
[ 1671.398] (EE) 8: /usr/lib64/dri/r600_dri.so (0x7ff6d2438000+0x528e86) [0x7ff6d2960e86]
[ 1671.398] (EE) 9: /usr/lib64/xorg/modules/extensions/libglx.so (0x7ff6d44d8000+0x4541a) [0x7ff6d451d41a]
[ 1671.398] (EE) 10: /usr/lib64/xorg/modules/extensions/libglx.so (0x7ff6d44d8000+0x39941) [0x7ff6d4511941]
[ 1671.398] (EE) 11: /usr/lib64/xorg/modules/extensions/libglx.so (0x7ff6d44d8000+0x3a183) [0x7ff6d4512183]
[ 1671.398] (EE) 12: /usr/lib64/xorg/modules/extensions/libglx.so (0x7ff6d44d8000+0x3c73e) [0x7ff6d451473e]
[ 1671.398] (EE) 13: /usr/bin/X (0x400000+0x3ad96) [0x43ad96]
[ 1671.398] (EE) 14: /usr/bin/X (0x400000+0x29e8d) [0x429e8d]
[ 1671.398] (EE) 15: /lib64/libc.so.6 (__libc_start_main+0xed) [0x7ff6d525c94d]
[ 1671.398] (EE) 16: /usr/bin/X (0x400000+0x2a1fd) [0x42a1fd]
[ 1671.398] (EE)
[ 1671.398] (EE) Bus error at address 0x7ff6ccbee000
[ 1671.398]
Fatal server error:
[ 1671.398] Caught signal 7 (Bus error). Server aborting
[ 1671.398]
[ 1671.398] (EE)
Please consult the The X.Org Foundation support
  at http://wiki.x.org
 for help.
[ 1671.398] (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information.
[ 1671.398] (EE)
[ 1671.398] (II) AIGLX: Suspending AIGLX clients for VT switch
[ 1671.460] Server terminated with error (1). Closing log file.