Created attachment 73422 [details]
Seemingly at random, the /usr/bin/X segfaults.
I am using Arch Linux with Kernel 3.7.3-1, KDE 4.9.95 (before you ask, yes I was running stable KDE at first), and x server 1.12. I also tried 1.13 (which was installed by default), the problem persisted.
Have an AMD HD7870 graphic card with proprietary 13.1 catalyst drivers installed.
Like I said, it happens randomly. Sometimes a day goes by, it does not happen. Other times it happens 10 times in an hour. Sometimes it happens twice per day.
I have also found that I could "invoke" the bug by clicking on the "Configure Kontact" option in Kontact, or by running a PDF kpartsplugin in Chrome.
What's interesting is that I see no errors in Xorg.0.log, but I do see seemingly relevant errors in kdm.log (attached).
Created attachment 73423 [details]
Created attachment 73424 [details]
my xsession-errors file
I think I'm having the same problem.
The crashes are also random, as described in OP comment. I'm also running the proprietary 13.1 catalyst driver on a 7970 GHz edition. I was running 12.11 beta before, but had some hard system freezes that where also related to x.org. The update did help, as such that x-server now restarts and doesn't kill the complete system.
I'm attaching my x.org logfile where the crash shows up, as opposed to OP.
Created attachment 73738 [details]
*** Bug 63845 has been marked as a duplicate of this bug. ***