Anita” post=89570\documentclass[a4paper,12pt,oneside,openany]{book}
\usepackage[latin1]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[italian]{babel}
\usepackage{pslatex}
\usepackage{amsmath, amssymb, amsfonts, amsthm, mathrsfs, cmll, stmaryrd, MnSymbol}
\usepackage{graphicx}
\usepackage[hang,small,bf]{caption}
\usepackage{listings}
\usepackage{bussproofs}
\usepackage{qtree}
\usepackage{fancyhdr,indentfirst}\theoremstyle{plain}
\newtheorem{thm}{Teorema}[section]
\newtheorem{cor}[thm]{Corollario}
\newtheorem{lem}[thm]{Lemma}
\newtheorem{prop}[thm]{Proposizione}
\theoremstyle{definition}
\newtheorem{defn}{Definizione}[chapter]
\theoremstyle{remark}
\newtheorem{oss}{Osservazione}\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\markboth{#1}{}}
\renewcommand{\sectionmark}[1]{\markright{\thesection\ #1}}
\fancyhf{}
\fancyhead[LE,RO]{\bfseries\thepage}
\fancyhead[RE]{\bfseries\footnotesize\nouppercase{\leftmark}}
\fancyhead[LO]{\bfseries\footnotesize\nouppercase{\rightmark}}\usepackage[sf,sl,outermarks]{titlesec}
\titleformat{\chapter}[display]
{\normalfont\Large\filcenter\fontfamily{pag} \selectfont}
{\titlerule[1pt]%
\vspace{1pt}%
\titlerule
\vspace{1pc}%
\LARGE\MakeUppercase{\chaptertitlename} \thechapter}
{1pc}
{\titlerule
\vspace{1pc}%
\Huge}\newbox{\riquadrobox}
\newenvironment{riquadro}[1]
{\setlength{\dimen255}{\parindent}%
\begin{lrbox}{\riquadrobox}\begin{minipage}{#1}
\setlength{\parindent}{\dimen255}}
{\end{minipage}\end{lrbox}\fbox{\usebox{\riquadrobox}}}
A parte le brutture contenute nel tuo codice, sulle quali non discuto, questo codice
`\documentclass[a4paper,12pt,oneside,openany]{book}
\usepackage[latin1]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[italian]{babel}
\usepackage{pslatex}
\usepackage{amsmath, amssymb, amsfonts, amsthm, mathrsfs, cmll, stmaryrd, MnSymbol}
\usepackage{graphicx}
\usepackage[hang,small,bf]{caption}
\usepackage{listings}
\usepackage{bussproofs}
\usepackage{qtree}
\usepackage{fancyhdr,indentfirst}
\theoremstyle{plain}
\newtheorem{thm}{Teorema}[section]
\newtheorem{cor}[thm]{Corollario}
\newtheorem{lem}[thm]{Lemma}
\newtheorem{prop}[thm]{Proposizione}
\theoremstyle{definition}
\newtheorem{defn}{Definizione}[chapter]
\theoremstyle{remark}
\newtheorem{oss}{Osservazione}
\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\markboth{#1}{}}
\renewcommand{\sectionmark}[1]{\markright{\thesection\ #1}}
\fancyhf{}
\fancyhead[LE,RO]{\bfseries\thepage}
\fancyhead[RE]{\bfseries\footnotesize\nouppercase{\leftmark}}
\fancyhead[LO]{\bfseries\footnotesize\nouppercase{\rightmark}}
\usepackage[sf,sl,outermarks]{titlesec}
\titleformat{\chapter}[display]
{\normalfont\Large\filcenter\fontfamily{pag} \selectfont}
{\titlerule[1pt]%
\vspace{1pt}%
\titlerule
\vspace{1pc}%
\LARGE\MakeUppercase{\chaptertitlename} \thechapter}
{1pc}
{\titlerule
\vspace{1pc}%
\Huge}
\newbox{\riquadrobox}
\newenvironment{riquadro}[1]
{\setlength{\dimen255}{\parindent}%
\begin{lrbox}{\riquadrobox}\begin{minipage}{#1}
\setlength{\parindent}{\dimen255}}
{\end{minipage}\end{lrbox}
\fbox{\usebox{\riquadrobox}}}
\begin{document}
$\mathfrak{D}$
\end{document}`
che corrisponde al tuo più l’ambiente [tt]document[/tt] con dentro il comando incriminato, non mi dà problemi. Non so come aiutarti, ma almeno so e sai che il codice funziona. Che distribuzione hai installato? Completa o parziale? Con quale sistema operativo lavori?