I searched online for this same message, and found several posts that said it had to do with Onedrive, and that you had to unlink Onedrive from your Microsoft account. It gave me the option to shut down anyway, and if I ignored it, it would just go back to my desktop. A few months ago, at shut down, I received a message that said something like, 'Task Host window is stopping background tasks'. I upgraded from Windows 8 to Windows 8.1 over a year ago.
