To write French in my Latex documents, I've added "\usepackage[utf8]{inputenc}" to the preamble.
This statement prints the following error in different parts of the log file:
Package inputenc Error: Unicode char (U+2060)
(inputenc) not set up for use with LaTeX.
...ci2002semantic}. ConQo \cite{Braun2008}
.bib
as it seems, then the issue probably arises from how you are accessing your bib file. Traditional BibTeX, e.g., does not do well with UTF-8.