...and one of them might be suing the other?
http://www.filmjunk.com/2010/08/18/battle-los-angeles-studio-planning-to-sue-directors-of-skyline/
(I say "yet another" cuz it's not exactly new: http://www.filmjunk.com/2007/03/07/when-movies-come-in-pairs-examples-of-hollywood-deja-vu/ )