I am using LNCS template to author a paper. But, weirdly at random point, if I add a \subsection a page break appears between 'Abstract' and 'First Section':
\documentclass[runningheads,a4paper]{llncs}
\usepackage{amssymb}
\setcounter{tocdepth}{3}
\usepackage{graphicx}
\usepackage{url}
%\urldef{\mailsa}\path|{alfred.hofmann, ursula.barth, ingrid.haas, frank.holzwarth,|
%\urldef{\mailsb}\path|anna.kramer, leonie.kunz, christine.reiss, nicole.sator,|
%\urldef{\mailsc}\path|erika.siebert-cole, peter.strasser, lncs}@springer.com|
\newcommand{\keywords}[1]{\par\addvspace\baselineskip
\noindent\keywordname\enspace\ignorespaces#1}
\begin{document}
\mainmatter % start of an individual contribution
% first the title is needed
\title{XXXXXX}
% a short form should be given in case it is too long for the running head
%\titlerunning{Lecture Notes in Computer Science: Authors' Instructions}
% the name(s) of the author(s) follow(s) next
%
% NB: Chinese authors should write their first names(s) in front of
% their surnames. This ensures that the names appear correctly in
% the running heads and the author index.
%
\author{}
%\author{Alfred Hofmann%
%\thanks{Please note that the LNCS Editorial assumes that all authors have used
%the western naming convention, with given names preceding surnames. This determines
%the structure of the names in the running heads and the author index.}%
%\and Ursula Barth\and Ingrid Haas\and Frank Holzwarth\and\\
%Anna Kramer\and Leonie Kunz\and Christine Rei\ss\and\\
%Nicole Sator\and Erika Siebert-Cole\and Peter Stra\ss er}
%
%\authorrunning{Lecture Notes in Computer Science: Authors' Instructions}
% (feature abused for this document to repeat the title also on left hand pages)
% the affiliations are given next; don't give your e-mail address
% unless you accept that it will be published
\institute{}
%\institute{Springer-Verlag, Computer Science Editorial,\\
%Tiergartenstr. 17, 69121 Heidelberg, Germany\\
%\mailsa\\
%\mailsb\\
%\mailsc\\
%\url{http://www.springer.com/lncs}}
%
% NB: a more complex sample for affiliations and the mapping to the
% corresponding authors can be found in the file "llncs.dem"
% (search for the string "\mainmatter" where a contribution starts).
% "llncs.dem" accompanies the document class "llncs.cls".
%
%\toctitle{Lecture Notes in Computer Science}
%\tocauthor{Authors' Instructions}
\maketitle
\begin{abstract}
Dummy abstract
\keywords{}
\end{abstract}
\section{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\section{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\section{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\section{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\subsection{XXXXXX}
\section{XXXXXX}
%\subsection{XXXXXX}% Uncomment this to see the problem
\end{document}
What surprising is, I am adding a \subsection at the end and the break appears at the very beginning, after the first page. Can anyone please give me any clue on how to fix it?