This X11 App requires the latest builds of X11 from http://xquartz.macosforge.org/trac/wiki in order to work. This X11 update will get overwritten whenever Apple updates X11 in either a software update or separately. For me, it's too much effort to bother updating X11 and potentially have it overwritten when 10.5.3 comes out. The interface in X11 doesn't look that nice anyway. Aparently there is a Mac native version in the works and I'll look at it again if that comes out.