GNOME Bugzilla – Bug 724928
gnome-shell crashed with SIGSEGV in __GI___pthread_mutex_lock()
Last modified: 2014-02-24 14:42:36 UTC
Open bug in Launchpad.net https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1281302 "Crash on login."
+ Trace 233211
Seems to be a VirtualBox bug to me.
Yes, looks totally like a bug in the virtual box graphic drivers.