(In reply to comment #16)
> No gnome-shell crashes since I've upgraded to Mesa 9.1.1. Will post an
> update in a few days whether it remains stable or I was just lucky today.

Observed the same gnome-shell crash problem with Mesa 9.1.1 with kernel
3.8.4-202 also.  The way how I reproduce this is to have dual monitors.  The
left one with resolution 1680x1050 (rotated counterclockwise) and the right
with 1920x1200.  With this setup, gnome-shell will always crash at initial
login.  If I don't rotate the left monitor, gnome-shell will not crash.