phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 2

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('3f1388ee6cb5a3f01907b29f3c1b3918', -1, 1257620190, 1257620190, '266bbf56', 17, 0, 0)

Line : 234
File : sessions.php