Does Craft support international urls? If I create an entry with international characters in urls? e.g. for Polish language?

If I create an entry with the word "ułatwienia" in the url, it doesn't work (I get Craft serving up the 404 page), I take out the special ł character and it's fine.

Although interestingly, the Live Preview url works fine with the special character included.

Have I missed something?
That should work fine and I just tested locally with a fresh Craft installation on the latest build and ułatwienia works in the slug for me.

Maybe you've got the limitAutoSlugsToAscii config setting set to true and ł gets changed to l in the slug, but you're still entering ł in the URL?