Alright, I just solved it. It was not a fonts cache problem, and I already tried that without success, but thanks, anyway. Also, newer Inkscape versions don't use a fonts.cache-1 file any more as far as I know, so that wiki page is probably at leas partially obsolete. But the problem apparently was ...

Hello, I have a problem with Inkscape 0.91 and Fonts. When I uninstall a Font in Windows, it remains usable in Inkscape, which is not a big problem in itself. But I am using the font " Last King Quest " in a personal project, which doesn't have the German umlauts ä, ö, ü. Being German, how...