Problem with \includegraphics in beamer — greek language doesn't work

Question

I use this code:

\documentclass{beamer}

\setbeamertemplate{navigation symbols}{}
\usepackage{subfigure}

\usepackage[english,greek]{babel}
\usepackage[utf8x]{inputenc}
\graphicspath{{/home/user/images/}}

\begin{document}


\section{intro}
\subsection{intro1}


\begin{frame}
\frametitle{test}
\setbeamercovered{transparent}

\begin{figure}

    \includegraphics[scale=0.5]{imag1}

\end{figure}

\end{frame}

\end{document}

and get 100 errors. The problem lies with \includegraphics; if I remove it it's OK. (The image is PNG and it is working with this layout in LaTeX.)

Is there some conflict with babel?

---------------UPDATED----------------------------------------

I noticed that in kile settings at the build section at the PDFLatex ,even though i had it to "xelatex" it showed "pdflatex" ,so i changed it again and now it works BUT now the greek language doesn't work!I can't see anything greek.I haven't changed anything!

--------------------UPDATED 2-----------------------------------------

\documentclass{beamer}

\setbeamertemplate{navigation symbols}{}
\usepackage{subfigure}

\usepackage[english,greek]{babel}
\usepackage[utf8x]{inputenc}

\newcommand{\gr}{\greektext}
\newcommand{\EN}{\latintext}

\begin{document}

Καλημέρα
\section{Ημέρα}

Καθόλου ελληνικά

\begin{frame}
\frametitle{test}
\setbeamercovered{transparent}

Καλησπέρα

\EN English \gr

\end{frame}

\end{document}

Answer 1

The updated example can't work with XeLaTeX. Here's a version that works

\documentclass{beamer}

\setbeamertemplate{navigation symbols}{}

\usepackage{fontspec}
\setsansfont{Linux Biolinum O}

\usepackage{polyglossia}
\setmainlanguage{greek}
\setotherlanguage{english}

\begin{document}

Καλημέρα
\section{Ημέρα}

Καθόλου ελληνικά

\begin{frame}
\frametitle{test}
\setbeamercovered{transparent}

Καλησπέρα

English

\end{frame}

\end{document}

Check the documentation of Polyglossia for the environments and commands that deal with language changes (they are not so important for beamer, as hyphenation shouldn't be used and \raggedright is in force).