I've just tried to use \frontmatter with memoir class for the first time and everything works fine except for some weird detail. When I add \frontmatter and \mainmatter commands, the numbers of subsections disappear in the ToC and also in the subsection titles themselves. The code is the following:
...
\chapterstyle{veelo}
\setcounter{secnumdepth}{3}
...
\begin{document}
\frontmatter
\include{abstract}
\include{acknowledgement}
\setcounter{tocdepth}{2}
\tableofcontents
\include{chap0_intro}
\include{abbrev}
\mainmatter
\include{chap1_somi}
\include{chap2_simulation}
...
ToC looks like this:

Why and how can I get them back while keeping the matter-commands?
memoircommand is:\setsecnumdepth{subsubsection}. – Alan Munn Jun 25 '12 at 19:12