Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live. - Martin Golding

UserGroup.class.php

<?php

class UserGroup extends BaseUserGroup
{
  /**
   * Overwrites the parent getName to return a translated string
   *
   * @return translated name as string
   */ 
  public function getName()
  {
    return (sfContext::hasInstance()) ? sfContext::getInstance()->getI18N()->__(parent::_get('name')) : '';
  }   
}

Note that without a symfony context, the code fails silently, returning an empty string instead of the group name. Awesome.