i finally managed to work through all issues that kept preventing builds. i hope this helps someone

  1. https://drupal.org/node/1812538 - make sure you ran ssh-keygen and have created a file at ~/.ssh/authorized_keys
  2. https://drupal.org/node/1659158 - delete any previous version of ~/.drushrc.php
  3. then build the machine which will have fqdn set because drush vsh worked during install - https://github.com/mitchellh/vagrant/issues/1456#issuecomment-16943974 and https://drupal.org/node/1659158
  4. i also had to change 'gid' => '100123', in ~/.drushrc.php - https://drupal.org/node/1705916#comment-7168594
  5. and use vagrant 1.0 not 1.1+ until the vagrant file config is adapted since the errormessage/warning causes the build to fail- https://github.com/mitchellh/vagrant/issues/1456