Quick fix for Joomla/Jomsocial registration form error

For a live website (Joomla/Jomsocial) we need an joomla expert to fix a error during registration. For the registration we've used the registration form from Jomsocial (3 steps). Most of the time this works fine, only in a couple of cases an error occure and the page keeps onloading. The following error is show via Firebug: <div id="errorboxheader">500 - DB function failed with error number 1062<br /><font color="red">Duplicate entry 'c84380aab4590a000eb7fc859bd1288e' for key 'PRIMARY' SQL=INSERT INTO `jos_community_register_auth_token` ( `token`,`auth_key`,`created`,`ip` ) VALUES ( 'c84380aab4590a000eb7fc859bd1288e','291b8f43c8e71aec9988df7cdce09b8a','2012-03-02 13:30:19','[login to view URL]' )</font></div> <div id="techinfo"> <p>DB function failed with error number 1062<br /><font color="red">Duplicate entry 'c84380aab4590a000eb7fc859bd1288e' for key 'PRIMARY' SQL=INSERT INTO `jos_community_register_auth_token` ( `token`,`auth_key`,`created`,`ip` ) VALUES ( 'c84380aab4590a000eb7fc859bd1288e','291b8f43c8e71aec9988df7cdce09b8a','2012-03-02 13:30:19','[login to view URL]' )</font></p> "NetworkError: 500 Internal Server Error -