Hi.
I'm mexican, so I speak spanish and my OS and files are mostly in this language.
KDE sets also spanish as default laguage, but, Kdenlive is always in english, that's OK for me. The thing is that when I work with a file (or ina folder) that have a tilde (or accent), like: "á, é, í, ó , ú" or an umlaut like "ü" in its name, in the rendered video, this particular file is replaced with an error screen with the legend "INVALID" Like this one:

I can work editing the files in Kdnlive just fine, the problem comes when I render them...
Is there any solution to this problem? or just trying to not use files and folders with this kind of characters?

Thanks, and sorry if my english is not perfect

This sounds very similar to this http://kdenlive.org/mantis/view.php?id=3017 bug.
It was fixed on the MLT side https://sourceforge.net/p/mlt/bugs/193/
You could submit a bug report to MLT