getting problem with enumerate environment i n beamer

dear friends
today while creating presentation in beamer, I faced a problem with using \begin{enumerate}\item \end{enumerate} environment in beamer with pdflatex. It simply not accepting it. given below the code
and error that I got
can anybody know what is this?


%mwcode 
\documentclass{beamer} 
\usetheme{Warsaw}
\usepackage{graphicx}
\usepackage{paralist}
\usepackage{amsmath}
\title[CloudComputing: SLA]{\bf Cloud Computing : Service Level Agreements (SLA)}
\author[A. S. Rumale, Dr. D. N. Chaudhari]{ {\bf Aniruddha S. Rumale}\\Assistant Professor, Computer Engineering\\
S.V.P.M.'s College of Engineering\\
Malegaon-bk, Baramati, Pune, India-413115\\
Email: \texttt{[email protected]}
}
\date{}
\begin{document}
\begin{frame}\titlepage \end{frame}
\begin{frame}\frametitle{Contents} \tableofcontents \end{frame}
\section{Abstract}
\begin{frame}\frametitle[SLA-Abstract]{Abstract: Service Level Agreements}
\begin{enumerate}
\item one
\item two
\end{enumerate}

\end{frame}





\end{document}
 
% errors on compilation in log file
! Undefined control sequence.<argument> .../enumerate \beameritemnestingprefix                                                   body endl.28 \end{frame}                The control sequence at the end of the top lineof your error message was never \def'ed. If you havemisspelled it (e.g., `\hobx'), type `I' and the correctspelling (e.g., `I\hbox'). Otherwise just continue,and I'll forget about whatever was undefined.
[3
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Aniruddha Subhashchandra RumaleMobile : 9890177859Flat 01, Anuj apartment,Amarsimha colony, Malegaon-bkBaramati, Pune 413115 ( MH ) Indiagreat people are those who cares to respond in genuine and gental way. and this is the only reason that your e-mail address is with me.thanks for your every response; that you showeredon my e-mails. asrumale
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