[plt-scheme] Problem fetching a URL

Hi,

I'm trying to fetch a URL using the code in the schematics cookbook but it 
is not returning the page and is instead giving an error message: "Missing 
Format Variable."  What am I doing wrong?

(require (lib "url.ss" "net"))

(display-pure-port
(get-pure-port
  (string->url 
"http://uk.old.finance.yahoo.com/d/quotes.csv?s=@%5EFTMC&f=sl1d1t1c1ohgv&e=.csv")))

Pasting the URL into my browser works correctly and also simpler URLs such 
as http://www.google.com/ do not give the same problem.

This is happening on version 3.52 of mzscheme running on Windows.

Thanks,

Ian