Ä & Ö - .lang issue

[Red]

As you might've noticed, I've been doing a little translation work, mainly, from English to Finnish.
However, there's an obstacle slowing my progress royally, which I call: Irritating Behaviour of Letters Ö & Ä; they do not work how I want, and seem only to rebel againts. Fortunately, they seem to work with German .lang files, so at least the potential for funcionality is assured, but this does not apply to rest of the languages, let alone custom made files. Is this more of a problem that can be equated with engine integration, or does it have something to do with additional fonts, or both? Help will be appreciated.