That is rather odd, looks like Rubygems isn't being loaded. Maybe you could add a ticket on github, and we can resolve it there.
Windows support is a few months off. We need it for Taskforce, so it's definitely going to happen. We basically waiting till WebKit 2 is stable. If anybody on this list know of Windows developers that would be interested in helping me, please let me know. I've never programmed on Windows before.
Alex