I have an Obi100 in use with Google Voice. Over the last 2 weeks or so, I have been unable to call ANY number that begins with 741 as the prefix. It rings once, then goes to a busy signal. I have verified these numbers to work with other phones also using Google Voice (but different accounts). I cannot seem to find a setting in GV or Obihai that would prevent this. I have rebooted my router as well as the Obihai.