Filecontents and newenvironment issue

Probably it's not the right way to use filecontents*, as egreg says in his comment.

Anyway, changing your MWE to

\documentclass[]{article}
\usepackage{listings}
\usepackage{filecontents}

\newenvironment{MyNewEnvironment}[1]{%
  \def\temp{#1}%
  \csname filecontents*\endcsname{\temp}%
}%
{\csname endfilecontents*\endcsname%
 \lstinputlisting{\temp}%
}%


\begin{document}

\begin{MyNewEnvironment}{foo.txt}
one
two
three
four
five
\end{MyNewEnvironment}

\end{document} 

works fine for me.

I suggest using fancyvrb and xparse, that allows also to pass options to \lstinputlisting:

\documentclass{article}
\usepackage{fancyvrb,xparse,listings}

\NewDocumentEnvironment{MyNewEnvironment}{O{}m}
  {\VerbatimOut{#2}}
  {\endVerbatimOut\lstinputlisting[#1]{#2}}

\begin{document}

\begin{MyNewEnvironment}[columns=fullflexible]{foo.txt}
one
two
three
four
five

\end{MyNewEnvironment}

\end{document}