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 ('a746bba9c81799f66b366e6a2c1f9993', -1, 1268420090, 1268420090, '266bbf55', 9, 0, 0)

Line : 187
File : sessions.php