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 ('2b588fa4261e60fa588876a0c5932e00', -1, 1369499802, 1369499802, '17164caa', 3, 0, 0)

Line : 187
File : sessions.php