Take the following blog page as a case:
!Careful, it has tons of youtubes embedded, so is a slow load! It is a Brazilian web page, written in Portuguese but hosted (according to the blog's owner) on a USA webhost.
Of interest are the "Pronúncia" links where they link to file names containing non ascii characters. Look at the second one (for Pará): the link as I write is to www.roney.com.br/wp-content/uploads/2010/06/par%E1.mp3 (unless he changes it out from under me in the future :)!))
As you see he has it coded, but what you don't know is what he actually named it on his file system or what system config they have.
If I click it in my Firefox browser I get their 404 page. He claims those links are working for Brazilian visitors. I thought this was a 100% server thing, i.e. either the server will serve it or it won't. Just for laughs I set the preferred language to Portuguese in my Firefox but as I suspected, it didn't make any difference.
Anyone care to offer any insight on how this might work in Brazil but not in USA or what things I would tweak on my own workstation so that they would serve for me too.