iRedMail-0.6.1，roundcubemail改完密码，会呈现空白页面～maillog出现以下信息，无法变更密码，请问如何解决呢～谢谢~

Nov  1 19:48:30 ms01 roundcube: PHP Warning:  require_once(Net/LDAP2.php) [<a href='function.require-once'>function.require-once</a>]: failed to open stream: 沒有此一檔案或目錄 in /var/www/roundcubemail-0.3.1/plugins/password/drivers/ldap.php on line 20

Nov  1 19:48:30 ms01 roundcube: PHP Fatal error:  require_once() [<a href='function.require'>function.require</a>]: Failed opening required 'Net/LDAP2.php' (include_path='/var/www/roundcubemail/:/var/www/roundcubemail/program:/var/www/roundcubemail/program/lib:/var/www/roundcubemail/program/include:.:/usr/share/pear:/usr/share/php') in /var/www/roundcubemail-0.3.1/plugins/password/drivers/ldap.php on line 20