I corrected the problem by editing the conform page at line 304:
i changed:
$_SESSION[$WA_sessionName] = mysql_insert_id();
to:
$_SESSION[$WA_sessionName] = mysql_insert_id($WA_connection);
I have a logged a bug for this issue, it seams on some servers, the connection used for the last insert is not assumed, so needs to be passed to the mysql_insert_id function.