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 ('0b3a7c94220ff8d4f087a06e8098b6e7', -1, 1268922678, 1268922678, '266bbf56', 32, 0, 0)

Line : 187
File : sessions.php