Since the move to libgtk 2.21.6 some applications like nautilus tend to crash segfault randomly. gdb show the segfaults happen on many gdk functions. Here are two differents backtraces for a same segfault happening in differents conditions.
http://pastebin.com/pue90cRC
http://pastebin.com/SjVsJN90
There are other segfaults that concern some other gdk functions but they are hard to reproduce because of the previous one.
Downgrading to libgtk 2.21.5 solve theses segfault. But there's now too many packages asking for libgtk 2.21.6 as a depency to be a viable solution. The strange thing is that if you previously compiled nautilus with libgtk 2.21.5 even if you update libgtk-2.0 to 2.21.6 then the problem is solved. Maybe this come from some missing headers in 2.21.6. I don't have any clue but this is what i've observed and what the backtraces tend to say.
This bug may concern some other gtk apps than nautilus, some apps using advanced drawing gdk functions.
It's a critical bug because nautilus is barely usable and even to get a window you have to pray for it to avoid the random crash at launch and after. Just change a theme and nautilus crash / restart. It happens very very often.
ps: reported upstream https://bugzilla.gnome.org/show_bug.cgi?id=628216
Thanks for the report, however there's no need to report a bug in Ubuntu if you already did it at the upstream bts. linking that report for now.