Well this is disappointing but looks to be necessary at this juncture.
From the FAA’s statement:
The FAA will work with the manufacturer and carriers to develop a corrective action plan to allow the U.S. 787 fleet to resume operations as quickly and safely as possible.The in-flight Japanese battery incident followed an earlier 787 battery incident that occurred on the ground in Boston on January 7, 2013. The AD is prompted by this second incident involving a lithium ion battery.
Their full Emergency Airworthiness Directive can be found here.