LaTeX can be quite nasty, yes it can. Todays feature:

! Package textcomp Error: Symbol \textcurrency not provided by
(textcomp) font family ptm in TS1 encoding.
(textcomp) Default family used instead.

l.16 ...ment --- wikipedia{,} die freie enzyklopä
die,

Basically boils down to using the German Umlaut ae=ä in the bibliography file. As soon as I'll find a better solution than removing it, I will post it here to. For now: remove it!