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 ('1c12da953bdf7e5a8f7f1e8bee78c020', -1, 1210723884, 1210723884, '26673f11', 0, 0, 0)

Line : 187
File : sessions.php