! Argument of contentsline has an extra }.
<inserted text>
                par
l.2 contentsline
                  {chapter}{chapternumberline {1}A Tale}{5}

documentclass{memoir}

renewcommand*{cftpartfont}{MakeTextUppercase}

% From Memoir manual p. 158
makeatletter
settocpreprocessor{part}{%
    lettempf@rtocf@rtoc%
    deff@rtoc{%
        texorpdfstring{MakeTextUppercase{tempf@rtoc}}{tempf@rtoc}}%
}
makeatother

usepackage{hyperref}

begin{document}

tableofcontents*

part{A Whale}
chapter{A Tale}
section{A Sail}
subsection{A Beachball}

part{A Poodle}
chapter{A Noodle}
section{A Doodle}

end{document}