Ecco un esempio che mi genera l’errore:
`
\documentclass[twocolumn,10pt]{report}
\usepackage[english,italian]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{microtype}
\usepackage{indentfirst}
\usepackage{graphicx}
\usepackage{anysize}
\usepackage{multirow}
\usepackage{array}
\usepackage{tabularx}
\usepackage{enumitem}
\usepackage{mdframed}
\usepackage{booktabs} \marginsize{2cm}{2cm}{2cm}{2cm}
\usepackage{fancyhdr} \pagestyle{fancy}
\renewcommand{\headrulewidth}{0.2pt}
\renewcommand{\footrulewidth}{0.2pt} \rhead{\small \ ProvaTex}
%%% Sfondo
\usepackage{eso-pic,graphicx} \makeatletter
\newcommand\BackgroundPicture[2]{ \setlength{\unitlength}{1pt}
\put(0,\strip@pt\paperheight){
\parbox[t][\paperheight]{\paperwidth}{ \vfill
\centering\includegraphics[angle=#2]{#1} \vfill }
} } \makeatother
\begin{document}
\begin{mdframed}
Prova minima
\end{mdframed}
\end{document}`
Ciao
Ricca