Reopened?? Received Another Letter from the Service Center.

Recived another letter form USCIS today after the 2nd RFE letter. It is an I-797C, Notice of Action.

"After review, we have reopened the above application or petition, or reconsidered the decision previously issued. You will recive a notice under seperate cover once all action has been completed."

What does this mean? Should I respond to the 2nd RFE anyway?