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 ('6adecfe4bd5f09d8f388a951764cba19', -1, 1268975504, 1268975504, '266bbf51', 0, 0, 0)

Line : 187
File : sessions.php