I am using Windows 8.1 with a Wireless Microsoft Keyboard & Mouse 7000, which uses same USB. Occasionally my keyboard stops working and only makes a click sound through my speakers, but the mouse works just find.
I am not for sure if this is connected, but this last time I had held down a key for long time before the keyboard stopped working. I do not know if the other times, when the keyboard stopped working, whither this was the case or not.
GeorgeT