Bad File Descriptor with FitNesse and RubyFit

This afternoon I was spinning up a RubyFit test in FitNesse when I encountered the following:

C:/lang/ruby/lib/ruby/gems/1.8/gems/fit-1.1/bin/../lib/fit/fit_server.rb:68:in `initialize’: Bad file descriptor

I was baffled, because everything looked fine. Turns out there is a bug in Java. So I upgraded to the latest version (I was on 1.5.0_13 and went to 1.6.0_03) and everything was fine after that.