[OS X TeX] memoir question

[Themis Matsoukas]

The commands \title and \pretitle in the example  below conflict if  
there is a line break in the title:

\documentclass[11pt,article]{memoir}
\pretitle{\begin{center}\sffamily\huge\MakeUppercase}
\posttitle{\par\end{center}\vskip 0.5em}
\title{Supplemental Handouts \\Solved Examples}
\author{Themis Matsoukas\\Penn State}
\begin{document}
\maketitle
\end{document}

1. if I remove the \\ from the title, the conflict is removed; or
2. if I comment out the \pretitle command, again the conflict is removed

The \posttile command does not interfere and the document typesets  
whether \postitle is commented out or not. For my immediate needs I  
have removed the \pretitle command, but can any one figure why the  
conflict?
The \pretitle and \posttile commands shown here are those that came  
with texshop in "LaTeX Preamble - Memoir customise".

Themis