So this is an error I am seeing quite a lot while developing Windows 8 Apps.
Luckily there is a workaround that seems to work every time (at least for me).
Simply(!) close down everything and log out. When you log back in make sure to use a full password (not a pin).
Fire up your project in Visual Studio and hopefully you will be good to go.
(Will post an update when I discover what is causing this error)