8老師,皮老師請教SR response email,???

Kid's 485,USCIS website showed approved status on 3/16/2012,but 3/20/2012 Department of Homeland Security eamil us that case is under review. what happened, what's wrong? Call them or do nothing, 8老師,皮老師請解答, 謝謝.

Time line as following:

3/6/2012, call USCIS and did SR.

3/16/2012  got 485 case update email: card production ordered,

3/19/2012 USPS pick up the card.

3/20/2012 SR response email from U.S. Department of Homeland Security:  Your case is currently under review.  You should receive a decision or notice of other action within 30 days of the date of this letter