Xorg crashed with SIGABRT in OsAbort()

[Lenka]

first reboot after upgrade failed, system frosen, second run well.

ProblemType: Crash
DistroRelease: Ubuntu 14.04
Package: xserver-xorg-core 2:1.14.5-1ubuntu3
ProcVersionSignature: Ubuntu 3.13.0-5.20-generic 3.13.0
Uname: Linux 3.13.0-5-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.13.2-0ubuntu2
Architecture: amd64
CrashCounter: 1
Date: Thu Jan 30 22:06:27 2014
ExecutablePath: /usr/bin/Xorg
InstallationDate: Installed on 2014-01-13 (16 days ago)
InstallationMedia: Mythbuntu 14.04 "Trusty Tahr" - Alpha amd64 (20140113)
ProcCmdline: /usr/bin/X -core :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
ProcEnviron:

Signal: 6
SourcePackage: xorg-server
StacktraceTop:
 OsAbort ()
 ?? ()
 FatalError ()
 ?? ()
 __libc_start_main (main=0x7f220d84a390, argc=9, argv=0x7fffbb404158, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffbb404148) at libc-start.c:287
Title: Xorg crashed with SIGABRT in OsAbort()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

[Apport retracing service (apport)]

StacktraceTop:
 ?? ()
 ?? ()
 ?? ()
 ?? ()