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 ('8e04d70e404024d9e650fe4975b0f4c5', -1, 1369423466, 1369423466, '6b1481d4', 1, 0, 0)

Line : 187
File : sessions.php