+1 prjdmd for the solution of using an older driver. I updated my driver to the latest and bluetooth disappeared from Windows 8.1 on my NUC. System restore did not even get it working again, nor did uninstalling the latest driver software. After seeing prjdmd's post I found the earlier driver (3.1.1307) on Dell's site and installed it. Bluetooth has now been restored.
-1 Diego_Intel for playing the blame the user game.