[tex-live] Problem with amsthm

[Cesar Romani]

What is wrong with the following code?:

--------------------
\documentclass[11pt]{book}
\usepackage[utf8]{inputenc}
\usepackage{amsmath, amsthm, amssymb, enumerate}

\begin{document}

\newtheorem{defi}{Definición}[section]

\newcommand{\cuatex}[3]
{\begin{center}
\setlength{\unitlength}{2.54cm}
\begin{picture}(#1,#2)
\put(0,0){\special{eps:quadrado.eps x=#1 in y=#2 in}}
\put(0,0){\framebox(#1,#2){\begin{minipage}{12.5cm}#3\end{minipage}}}
\end{picture}
\end{center}}

\newcommand{\Defi}[2]
{\cuatex{5.2}{#1}{
\begin{defi}
#2
\end{defi}
}}

\chapter{Capítulo I}
\section{Sección 1}
This is only a test.

\Defi{2.1}{Diremos que un conjunto no vacío $X$ es un espacio métrico,
si sobre él está definida una función
$$
d:X\times X \to \mathbb{R}
$$
satisfaciendo las siguientes propriedades
\begin{itemize}
\item $d(x,y)=0$ si, y solamente si $x=y$.
\item La función $d$ es simétrica, esto es, $d(x,y)=d(y,x)$
\item $d(x,z)\leq d(x,y)+d(y,z)$ (desigualdad triangular)
\end{itemize}
La función $d$ es llamada métrica.
}

\end{document}
--------------------


Each time I run it with latex or pdflatex, I always get:

--------------------
! LaTeX Error: Something's wrong--perhaps a missing \item.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
  ...

l.40 }
--------------------

If I remove amsthm from the \usepackage, it compiles fine, but I would
like to have it included. I think it is a conflict with amsthm.sty. Is
there are workaround for it?

Many thanks in advance,

-- 
Cesar