\documentclass[12pt]{article}

\usepackage{calc}

%\newenvironment{structproof}
%{\begin{list}{\structproofnum}{}

\newcommand{\test}{0}
\newcounter{ctr}
\setcounter{ctr}{\test}

\begin{document}

	test is \test

\arabic{ctr}
\stepcounter{ctr}
\arabic{ctr}

\begin{minipage}{1in}
\stepcounter{ctr}
\arabic{ctr}
	\renewcommand{\test}{3}

\newcommand{tester}{\arabic{ctr}}

	test is \test

\end{minipage}

	test is \test

\arabic{ctr}

this is very strange.  Why are the lines so close together?
Perhaps it is some problem with using 12pt font.
No, I think it is a problem with minipage.


\end{document}