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 ('e0d70633e76ffe017d8ef81fb882dcd7', -1, 1268252206, 1268252206, '266bbf55', 4, 0, 0)

Line : 187
File : sessions.php