I received the same type of call. You answer, but total silence on the other end.

Received a call from Bolin Real Estate on 3/14/08 at 01:00 in the morning. When I said hello atleast 3 times, no response from caller.They apparently use other numbers as I have received a call earlier on 4/6 at 01:00 in the morning from phone number: 940-891-6368. This is really getting old.