Use biblatex and utf8

Don't use utf8x. Load the TS1-encoding e.g. through textcomp and if you don't like the euro you get with textcomp change the definition of \texteuro. E.g.:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{textcomp}
\usepackage{eurosans}

\begin{document}
€  \let\texteuro\euro €
\end{document}

The utf8x option for inputenc is (probably) the issue here. Try just

\usepackage[utf8]{inputenc}

and you should be fine (as detailed in the biblatex manual).