phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '848d9c87e08e2a2e4d14c57c37f61e15' 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 ('848d9c87e08e2a2e4d14c57c37f61e15', -1, 1397780851, 1397780851, '36c624b3', 15, 0, 0)

Line : 245
File : sessions.php