> It seems that Tk does not manage to obtain this font on my system.

This means that the X11 font handling has a severe bug. I think that the functions InitFont(), GetFont(), TkpGetFontFromAttributes() in tkUnixRFont.c are responsible. Another important function is TkpGetFontFamilies(), is this function recognizing the font? Can you figure out where it fails? Unfortunately (!) under my system the font handling works.