White Screen Page When roles Changed! [Solution]

He is the solution White Page when changing Roles from Admin to rest of Roles:

En: mvb_wp_access.php, replace the function render_optionlist() with :

public function render_optionlist() {
  $role = mvb_Model_Helper::getParam('role', 'POST');
  $user = mvb_Model_Helper::getParam('user', 'POST');
  $m = new mvb_Model_ManagerAjax($this, $role, $user);
  $return = $m->manage_ajax('option_list');
  foreach($return as $a => $b)
    $return[$a] = utf8_encode($b);
  die(json_encode($return));
}

Good Luck

http://wordpress.org/plugins/advanced-access-manager/