Is there some maintenance job done during that time or so (04:00 till 05:00 Bluehost local time).
Over the last month or so each day when I try to upload fresh content to my website I can't connect to my FTP, shortly after 13:00 CET everything works fine again.
My site itself is online during that time, it's only FTP and sometimes acces to the control panel thats down during that hour.