I don't think it has anything to with UAC. I install most of my games to a separate hard drive (therefore outside of program files directory). I'm using Windows 8.1 64-bit, tried launching The Bureau: XCOM Declassified (DX11) but was not successful. Did not have any issues with DX9 games though. The main issue is dxgi.dll, it has been updated with the 8.1 update. So the dxgi.dll with the SweetFX bundle needs to be updated as well. Hopefully all of our problems will be solved when eFX comes out. I wish we could have an adaptive injection method like the one in RadeonPro.