Updated the Lubuntu from 13.04 to 13.10 on my MacBook Air. Ever since, when I open up the lid after standby, the system wakes from standby but after a few seconds it goes into standby again. There seems to be another (new) process putting my device into sleep mode now, too.
If I kill xfce4-power-manager, it only goes to standby once. However, it shouldn't go into sleep at all when xfce4-power-manager is not running.
How can I track down the new trigger of the standby mode?