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 ('2a8351a2bd585aaba7fcf1fa3b5c89c9', -1, 1369132075, 1369132075, '36ea2a10', -9, 0, 0)

Line : 187
File : sessions.php