Windows® 8 Cliffs of Dover Fix (is here).

[TonyD]

John, here’s a method for excluding files in your AV: Link The file name I’d suggest is ‘CloD*.*’ which should exclude all the files; if this doesn’t work you will have to add each separately. Both ‘CloDer.exe’ and ‘CloDer.dll’ must be in the same folder (I put them in the game folder) for the exe to work. You then run ‘CloDer.exe’ while Steam is running and it should start.

I don’t know why Smart Screen is being triggered as I don’t use Internet Explorer, but you could have a look here