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 ('2837fd442b65c0165d6dde8cc0b464ea', -1, 1257634596, 1257634596, '266bbf58', 7, 0, 0)

Line : 234
File : sessions.php