I thought you might have written the server, since their isn't too much fat in the HTTP headers :) You should add a Server header for bragging rights though.
Congrats to you and your team on launching the first Arc app regardless of how much of the stack is written in Arc.
I'm having trouble using drakma to hit the site. I'm pretty new to Lisp so I'm still learning what I'm looking at, however it looks like something in the stream from the server (possibly while reading headers?) is messing up CHUNGA:READLINE which Drakma uses.