I tried with VapourSynth Editor (says it can't load script resources on startup) and with my VapourSynth Multi-Viewer (fails to load vsscript.dll)
http://www.vapoursynth.com/2014/08/a-new-editor/
If I have to read the DLL path from the registry, then I can do that.
...
but also it's failing to open in a video player; and even vspipe.exe is failing on a basic "blankclip" script
I'm using Windows 10 x64