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 ('8c842664979ef6c5796d94e8c9f446d5', -1, 1417162478, 1417162478, '36571e02', 30, 0, 0)

Line : 187
File : sessions.php