The font-installer in KDE 3.5.7 (Slack 12) works fine, but for one font, in which case it cannot pick the name of the font. In KDE 3.3, this font was installable without problem. The font in question is here: http://ftp.debian.org/debian/pool/main/t/ttf-nafees/
And the name of the font is supposed to be "Nafees Web Naskh"