Two of those promising new nearby exoplanets—Gilese-581g and 581d—may have never existed. Instead of being the second- and third-closest potentially-habitable planets, these former candidates for extraterrestrial life were likely nothing more than tricky sunspots.
(Apparently this may not be a revolutionary result, as other researchers have been doubting 581g's existence for years.)
The same technique (spectral analysis to track superheated hydrogen and sodium emissions from the star) simultaneously confirmed that at least 3 other exoplanets in the system (Gilese-581b, c, and e) are indeed legitimate planets. And as Gilese-581c was recently added to the "potentially habitable" list, the system as a whole retains plenty of promise.
You can read more at space.com