You are saying that you have multiple Ruby installations on your PC but RiS defaults to the wrong one (or do you mean you copied ruby.exe alone under /Program Files)?
exactly, it doesn't matter if file is actual ruby.exe, it works with 0 bytes size C:\Program Files\ruby\bin\ruby.exe
the way I described before (i.e. picking correct installation).
I have ruby installation in C:\ruby186, C:\ruby187, and C:\ruby190.
Have you tried creating a new Solution? It may be that the project config is causing problems. To see if that is so, try creating a completely fresh project with a very simple
'hello world' Ruby program and let us know if this has any problems.
Yes, I tried, actually I've got about 5 such empty solution already