phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 2

INSERT INTO phpbb2_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('d69f0d0ddb8b9ce2a6075e29e8899a95', -1, 1268337431, 1268337431, '266bbf58', -2, 0, 0)

Line : 187
File : sessions.php