that's what I said , I tried changing the project's properties. See here:http://screencast.com/t/bXAAl3Ifox
I could not change it there so that it would stick, note that there does not seem to be an "apply" button, so I tried just saving all . Anyhow, I gave up and put a Ruby distribution where it seems to want it.
Not a great solution obviously if I'm trying to test different Ruby releases .