phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '77a987e98bc2d0615a4864ab99ac4d47' for key 'PRIMARY'

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('77a987e98bc2d0615a4864ab99ac4d47', -1, 1412187601, 1412187601, '32119a10', 15, 0, 0)

Line : 245
File : sessions.php