The newest update cogl (1.8.0-1) in Precise repos breaks Gnome-shell. It will lead into a desktop with no panels. I think clutter and/or mutter dies.
So, like usually, downgrading to previous version (1.8.0-1~svn1) solves this issue. Or even better, do not upgrade yet if you are using Gnome-shell.
I have Gnome-shell from Ricotz Testing PPA (Precise) and it died too.