Note in the duplicate bug #1203593 the stacktrace from apport doesn't match the crash; from the Xorg.0.log the crash would be in sna_accel_flush_callback().
Can you please make sure you run "apt-get install xdiagnose" and attach all logs if this reoccurs.
Note in the duplicate bug #1203593 the stacktrace from apport doesn't match the crash; from the Xorg.0.log the crash would be in sna_accel_ flush_callback( ).
Can you please make sure you run "apt-get install xdiagnose" and attach all logs if this reoccurs.