Check for X server doesn't work with pyGTK >= 2.10
Gajim's code which checks that an X server is present doesn't work with pyGTK 2.10 and later, since it no-longer throws an exception, but just a warning, it's outlined here: http://live.gnome.org/PyGTK/WhatsNew210#head-34d574e59e1aa42cb14e7499ac557446b2c90f83