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 ('9ebbb0cae2fb209c1c810d8be4afe8db', -1, 1231539350, 1231539350, '26673f39', 1, 0, 0)

Line : 172
File : sessions.php