Happened to me couple of times in talkatone / GV in android, and Obi+ IPkall-> callcentric (line 2) set up, calling from outside with cell phone, It happened to me last couple of days on talkatone suggests that the problem is probably not just IPKall or Obi100 issues.
I suspect the problem is more of google voice rather than cable modem/router/Obi issues. Any way, rebooted modem/router/obi100,
I just wonder whether google voice can maintain the reliability quality after May 15, 2014. Porting GV phone number would be the last thing I want.