phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO phpbb2_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('e7261a97e1b6e8cbc439c3694e402061', -1, 1268376961, 1268376961, '266bbf59', 10, 0, 0)

Line : 187
File : sessions.php