webrick works fine but lighttpd breaks on the most simple issue

I've spent four hours trolling google search results and have scoured
my own logs and can find nothing.

Until recently I used Webrick for all my http server needs. Now I'm
going live to the outside world. So I download lighttpd-1.4.13.tar.gz
and perform ./configure and make install. I add /usr/local/sbin (where
lighttpd lives now) and I'm done. Fastcgi is built-in so I install no
other stuff.

I go to the top level of my ROR app (/home/smiller/beamon-erp) and
perform: script/server

Since lighttpd is on path it runs it instead of webrick. Realizing
there's no lighttpd.conf in my config directly, it copies one in from
/usr/local/lib/ruby/gems/1.8/gems/rails-1.1.6/configs/lighttpd.conf and
then is off and running just fine.

I start my browser (firefox on RH linux) to localhost:3000 and I
immediately get this error: