According to another website - and in a message from the website, not from a complainant - this is a "spoofed" or fake number. No info on what the "message" purports to be. Best advice from many sources is: do not pick up calls you do not recognize. If they don't leave messages, forget them.
Got a call from 571-963-3217 yesterday (May 23, 2012) and today. Caller ID said it was from Virginia. When I answered no one responded then the automatic phone line voice came on saying that if I wanted to make a call, please hang up. Today I tried to call the number back and a computer voice said that the call could not be completed.