hibernate greyed out on xubuntu 12.10

sudo nano /etc/polkit-1/localauthority/50-local.d/com.ubuntu.enable-hibernate.pkla

Fill it with this:

[Re-enable hibernate by default]
Identity=unix-user:*
Action=org.freedesktop.upower.hibernate
ResultActive=yes

Some users will then need to run sudo update-grub to get the hibernate option to be available in the power menu...