Beamer에서 XeTeX을 쓸 때 아래와 같이 \fontspec 명령이 작동하지 않는데 이것은 왜 그런 것인가요?

% !TEX TS-program = xelatex

% !TEX encoding = UTF-8 Unicode

%

% (c) 2008, Eung-Shin Lee

% public domain.

%

\documentclass[10pt,compress,slidetop,%

xcolor={svgnames},% sub-package options

t]{beamer}

% 이곳에서는 글씨체의 크기를 10 pt로 하였음,

% t는 본문 내용이 슬라이드의 위(top)부터 시작

%

% Beamer 저작권

% Copyright 2004 by Till Tantau <tantau@users.sourceforge.net>.

% and 2005-2006 by Jorg Cassens <jorg.cassens@idi.ntnu.no>

%

\mode<presentation> % 출력 양식을 프레젠테이션으로

{

\usetheme{Frankfurt} % 템플릿은 프랑크푸르트로

% 템플릿 종류:

% Antibes, Bergen, Berkerley, Berlin, Boadilla, Copenhagen, Darmstadt,

% Dresden, Frankfurt, Goettingen,

% Hannover, Ilmenau, JuanLesPins, Luebeck, Madrid, Malmoe, Marburg,

% Montpellier, PaloAlto, Pittsburgh, Rochester,

% Singapore, Szeged, Warsaw

%

\usecolortheme[named=olive]{structure} % 색상 결정

\usefonttheme[onlymath]{serif} % 수학공식에서 사용하는 글씨체

% \useoutertheme{infolines}

% or whatever

\setbeamercovered{transparent} % overlay 사용

% or whatever (possibly just delete it)

}

%================== 필요한 패키지 설정 ===============

\usepackage{verbatim}

\usepackage{pdfpages}

\usepackage{multimedia}

\usepackage{animate}

%

\usepackage{bm}% bold math

\usepackage{amsmath,amssymb,amscd}

\usepackage{subeqnarray}

\usepackage{mathptmx}

%

\usepackage{helvet}

\usepackage{courier}

\usepackage{relsize}

%

\usepackage{colortbl}

\usepackage{wasysym}

%

\usepackage{tikz}

\usetikzlibrary{arrows,shapes,calc,patterns}

\tikzstyle{every picture}+=[remember picture]

\usetikzlibrary{%

decorations.pathreplacing,%

decorations.pathmorphing%

}

% ================== 한글 사용 =====================

\usepackage[itemph]{xetexko-var}

%%% 입력파일이 UTF-8 인코딩이면 다음 행을 삭제하십시오.

%\XeTeXinputencoding=euc-kr

\setmainfont[Mapping=tex-text]{Minion Pro}

\setsansfont[Mapping=tex-text]{Myriad Pro}

\setkormainfont(나눔명조 Bold)(궁서){나눔명조}

\setkorsansfont(나눔고딕 Bold)(궁서){나눔고딕}

%==============================================

%

%================ dual screen =======================

%\setbeameroption{show notes on second screen=left}

%\setbeamertemplate{note page}[compress]

%==============================================

%

%================ 제목에 사용할 글씨체 설정 ==============

\setbeamerfont{title}{shape=\itshape,family=\rmfamily}

\setbeamerfont{frametitle}{family=\rmfamily}

%\usepackage[T1]{fontenc}

% Or whatever. Note that the encoding and the font should match. If T1

% does not look nice, try deleting the line with the fontenc.

%===============================================

%

%================== 표지 만들기 =====================

\title % (optional, use only with long paper titles)

{Beamer 프레젠테이션 활용}

\subtitle{\LaTeX 기초강좌 (2008년 가을, 공주대학교)}

\author{홍길동 } % 저자(발표자)

% Till Tantau\author{{1} \and

% J\"{o}rg Cassens\inst{2}

\institute[]% (optional, but mostly needed) 소속기관 약자 표기

{자신의 소속 기관} % 표지에 나타나는 소속기관 full name

% - Use the \inst command only if there are several affiliations.

% - Keep it simple, no one is interested in your street address.

\date[08-11-09]% (optional, should be abbreviation of conference name)

{} % 날짜 지정: \today

% - Either use conference name or its abbreviation.

% - Not really informative to the audience, more for people (including

% yourself) who are reading the slides online

\subject{Beamer}

% This is only inserted into the PDF information catalog. Can be left out.

% Delete this, if you do not want the table of contents to pop up at

% the beginning of each subsection:

%===============================================

%

% ==================== 차 례 ======================

\AtBeginSection[]

{

\begin{frame}<beamer>

\frametitle{차 례}

\tableofcontents[currentsection,hideallsubsections]

%\tableofcontents[currentsection,currentsubsections]

\end{frame}

}

%===============================================

%

%

%================== 본문 시작 ==========================

\begin{document}

%

%================= 표지를 화면으로 나타나기 ===========

\begin{frame}

\titlepage

\end{frame}

%===============================================

%

% ******************************

\section{Introduction}

%*******************************

%

%------------------------- 슬라이드 ------------------------

\begin{frame}

\frametitle{나의 살던 고향은}

\fontspec{맑은 고딕}{그 속에서 놀던 때가 그립습니다.}

\end{frame}

%------------------------------------------------------------

%

\end{document}

%==================== 본문 끝 = ===========================