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 ('2e8d1c4006214bd7a6c478c37dc97d24', -1, 1269252637, 1269252637, '266bbf57', 39, 0, 0)

Line : 187
File : sessions.php