That ñ is not working is not a bug, savegame names can not contain non-Latin letters, which is an OS limitation I assume. The error message should be more informative though I think.
I run Windows 7 64 bits and a 64 bits version of Factorio, latest version if that makes a difference.
I don't know ...

Well, first of all, I want to say that this doesn't deserve a priority fix at all, buy I wanted to let the devs know anyway.
Also, forgive me if this was already reported, I searched as in every way I could think of about this issue but nothing showed up, if it is please delete this topic.
Doesn't ...