Xubuntu 12.04 : failed to hibernate session not authorized

Suspend was working, but hibernate was sowing message : "failed to hibernate session not authorized".

I have created file /etc/polkit-1/localauthority/50-local.d/com.ubuntu.enable-hibernate.pkla


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

Now hibernate is working fine.