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I just followed these exact steps: Deleted SF Folder. Restored default window layout. Restarted Unity. Installed SF from asset store:

I can confirm I'm also getting this error again on 2017.2.0f3 - ShaderForge will not open/load.  I had to re-install Unity 5 and create a temp project just to create a shader and import it into my 2017 project :-/ Is there a final fix for this ever persistent issue?