Xubuntu 13.10: disabling suspend on lid being closed
Solution 1:
I had the same problem, affecting the power button as well. This worked for me:
https://wiki.archlinux.org/index.php/xfce#xfce4-power-manager
/etc/systemd/logind.conf
HandlePowerKey=ignore
HandleSuspendKey=ignore
HandleHibernateKey=ignore
HandleLidSwitch=ignore