Rendering umlauts fails

[Michael Käppler]

Hi all,
after using Lilypond a long time on a Linux machine I now tried out 
the Win build. There I encounter a problem which I have never seen 
on Linux AFAIK. If I use Lyrics containing umlauts, sometimes Lily
only doesn't show them, sometimes aborts with plenty of messages like this:

Programmierfehler: invalid UTF-8 string
Fortsetzung, die Daumen drücken

It also reports:

Programmierfehler: Glyph hat keinen Namen, aber Zeichensatz unterstützt 
Glyphnamen.
Glyph U+FFFFFFFF wird übersprungen, Datei C:/Program Files 
x86)/LilyPond/usr/share/lilypond/current/fonts/otf/CenturySchL-Roma.otf

I've set enc=utf8 in my vimrc.

Regards,
Michael