Ok so now I get this, what I don't understand is that it seems to be complaining about the NET framework version, but I can play aurora no problem so I should have that framework installed and working already.
OK, that makes sense. Windows won't load web-downloaded assemblies by default. Which explains why the devs never encountered this.
There's a few options but the simplest is to make the change in the code.
Try the new debug build attached. If it works I'll update the main release build attachment.
Edit: To clarify, this is a CAS policy issue, not really a .NET Framework issue. It just so happens that the .NET Framework version on your machine has that default policy in place to disallow foreign DLL loads (which I suspect is most people). The testing I did with a fresh VM was a VM oriented towards Microsoft developers (the only way I could get quick access to a VM image), so it probably had more open CAS policies in place.