WinXP, FF 3.6
For instance, if I want to have feed for "Category:Náchod" on cs.wikipedia, this resolves in error called "Something's wrong!". Here is a link to the category: http://cs.wikipedia.org/wiki/Kategorie:N%C3%A1chod
Here are links that give the error:
However, I realized just not that once I substitute the "á" with "%C3%A1" in the URL then it works. The problem is probably your tool can not translate special chars into this code. This is not nice since it forces the user to rearch for the translatins themselves.
The "á" is pretty common letter in Czech language.