"Undefined Control Sequence" error for several lines

Question

I get "undefined control sequence" error message for several lines: "undefined control sequence" (after "\pagebreak", where I pressed ENTER for an empty line), "undefined control sequence \section", and "undefined control sequence \end{document}".

It is the first time that I installed TeXstudio on Windows 7. I also installed MiKTeX prior to TeXstudio. Moreover, I tried the code on Windows XP and didn't get the error messages at all.

The complete code is below.

\documentclass[a4paper]{article}
\usepackage{graphicx,float}
\floatstyle{boxed}
\usepackage[toc,page]{appendix}
\usepackage{hyperref}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{textcomp}
\usepackage{multirow}
\usepackage{natbib}
\usepackage{tikz}
\usetikzlibrary{decorations.pathreplacing}
\usetikzlibrary{decorations.pathmorphing, patterns,shapes}
\usepackage{preview}
\usepackage[affil-it]{authblk}
\usepackage{amsthm}
\newtheorem{proposition}{Proposition}
\newtheorem{lemma}{Lemma}


\title{the title}
\begin{document}
\date{March 4, 2014}
\maketitle
\pagebreak

hi

\section{Intro}

This is the main text.

\end{document}

Answer 1

The following minimal example replicates the problem:

\documentclass{article}
\usepackage{tikz}
\usepackage{preview}

\begin{document}

This is the main text.

\end{document}

It's obviously a bad interaction (incompatibility) between tikz and preview. Either drop the loading of preview, or load it with the [active] package option.