Оригинальный сообщение: David ,
Are you using Windows 10? If so, this seems to be a very big bug that's been floating around since late 2015. I'm trying to find a solution, too. If you press Control-Alt-Delete, do you get a blue screen with options like "Lock", "Sign out", and "Task Manager?" If so, can you start Task Manager? Maybe you can see some programs running there that shouldn't be.