[racket] Problematic code...

The code found at:

http://docs.racket-lang.org/more/index.html

Worked for me at one point quite a while back but no longer. I'm
running on Windows Vista with the latest version of Racket. Neither
the original code with the simple (but flawed) serve nor the 'fixed'
version provide anything that my browser can see. The original
resulted in a permanent 'loading' message and the second provided the
less than illuminating: Oops! Firefox could not connect to
localhost:8081. The code was copied from the complete text version so
I am reasonably sure that it is not a typo. As I said, this once
worked and I'd like to run through the intro again before going on to
the more advanced versions available. I'm very good at making faulty
assumptions and tiny errors so I'm perfectly willing to believe that
the screw-up is in something that I've done (or not done as the case
may be). Any help? Advice?

--hsm