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 ('5787023b3d48a090357cc2cc55c7044b', -1, 1397685196, 1397685196, '6ca2d44b', 44, 0, 0)

Line : 187
File : sessions.php