Hanging Website: TCP Problem?

[Aaron VanDevender <sig netdot net>]

I was trying to visit the website www.nap.edu (National Academies Press)
using my FC6 desktop machine, but firefox just grinds on it indefinitely
with "Waiting for www.nap.edu...". I can telnet to port 80 of the site,
and it connects, but after saying "GET /" it just hangs, and never
returns anything.

This would seem like a problem with their site, except that I tried it
with an FC3 machine (kernel-2.6.12-1.1381_FC3) and was able to surf
normally. I also tried telneting to port 80 from the FC3 machine, and
"GET /" immediately returned the correct front page to the site.

I thought that it might be the an ECN problem, but it is set to 0 on my
machines. I've seen the bad behavior on two separate FC6 machines, so I
don't think it's a fluke.

Dose anyone know what might be causing this site to hang with FC6?

-Aaron