system freeze after resume from hibernate/suspend

[scar]

Well, my system is partially frozen, when I try to resume from hibernate/suspend.
It happens only to sessions opened via lightdm.
When the system finishes resuming, I get the desktop back, but the system does not respont to anything except the mouse.
Hard reboot is required.

I can still suspend/hibernate and resume correctly from the lightdm login screen, from a tty console, from any graphical session opened without lighdm (i.e.: with startx).

It happens on arch linux 64 bits, with:

lightdm 1:1.8.1-1
pm-utils 1.4.1-6