I am using the Win8 Store Sample UI transcode app under Windows 8.1. The application is a fresh build after a fresh install of the Media SDK 2013 R2.
Using Visual Studio 2012 to debug the app I get the exception : Platform:COMException ^ at memory location 0x0035F6EC. HRESULT: 0x80040150. This value is defined as "unable to read the registry". I am running the app from VS as admin.
I was able to build this application and run it fine on this system a month ago with the same drivers that I am currently using. Attached is my system config.