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) VALUES ('8de691923dd63384de7aa00652bc61e6', -1, 1408580554, 1408580554, '36e2a650', 20, 0)

Line : 315
File : sessions.php