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 ('911828d28a81f78825cca64d3d7b1adf', -1, 1397981918, 1397981918, '36c614d7', 26, 0)

Line : 170
File : sessions.php