phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO mex2mex_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in) VALUES ('ad6f0885e90139c39b0f88a705a9365c', -1, 1406688986, 1406688986, '36d3d50a', 9, 0)

Line : 170
File : sessions.php