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 ('3cd31ea08a1633095020c11bb32e355f', -1, 1397826407, 1397826407, '36c4c448', 8, 0)

Line : 170
File : sessions.php