I am using MiKTeX 2.9 and XeLaTeX. Here is my minimal working example:
\documentclass[11pt,a4paper,roman,english]{moderncv}
\moderncvstyle{classic}
\moderncvcolor{blue}
\usepackage[scale=0.75,a4paper]{geometry}
\usepackage{xunicode}
\usepackage{xltxtra}
\setmainfont[Mapping=tex-text]{Times New Roman}
\newfontfamily{\cyrillicfonttt}{Courier New}
\usepackage{polyglossia}
\setmainlanguage[babelshorthands=true]{russian}
\setotherlanguage[variant=us]{english}
\usepackage{fontawesome}
\newfontfamily{\FA}{FontAwesome}
\newcommand\faSkype{{\FA\symbol{"F17E}}}
\firstname{John}
\familyname{Smith}
\title{TeX writer}
\extrainfo{\faSkype~ myskypelogin}
\begin{document}
\makecvtitle
\end{document}
Skype Font Awesome symbol has been created like in this question. But for some strange reason it doen't work properly:

What am I doing wrong? I have tried to replace "F17E with "F117 and it worked just fine.