The Previous attack involved the Stuxnet virus. It attacked the computers at the installation and ran a program that sent the atomic processes there into a self destructing cycle, damaging the plant.
http://www.telegraph....owers-and-Israel.html
It has been reported another similar virus has been developed. Perhaps this has attacked the second plant.
Unless you are Iranian, it sounds like a win-win scenario. Irans nuclear ambitions are slowed down or stopped, and a full blown Israeli military attack (and the dire consequences) are averted.