Back from vacations and it's looks like the issue is not or not entirely in kernel.
I'm back to 3.13.0-24-generic and just installed gnome-shell 3.12 and the problem is gone. I can now safely close and open the lid.
So, looks like that at least a 'trigger' for the freeze is somewhere in Unity/compiz.
Gonna try again several different kernels.
Back from vacations and it's looks like the issue is not or not entirely in kernel.
I'm back to 3.13.0-24-generic and just installed gnome-shell 3.12 and the problem is gone. I can now safely close and open the lid.
So, looks like that at least a 'trigger' for the freeze is somewhere in Unity/compiz.
Gonna try again several different kernels.