Conflict with Natbib [closed]

Question

I am currently writing my thesis and I've ran into a problem while increasing the complexity of the packages I needed to use. I was originally using the \cite{} macro to do all the references but I needed some more functionality hence I opted for the natbib package. Unfortunately when I try to compile the tex file I get the following error:

/usr/local/texlive/2011/texmf-dist/tex/latex/natbib/natbib.sty:739: LaTeX Error: Command \citetext already defined.
           Or name \end... illegal, see p.192 of the manual.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.739 ...ommand\citetext[1]{\NAT@open#1\NAT@close}

I think that the natbib package might be conflicting with another package that already defines the \citetext key, but how can I tell? I've tried a process of elimination but wasn't able to track down the offending package - if it even is that case - . The packages are imported into the main tex file with \input{packages} and include:

%%%%%%%%%%%%%%%%%%%%%%
%% Declare packages %%
%%%%%%%%%%%%%%%%%%%%%%

\usepackage{ccaption, graphicx, textcomp, tabularx, booktabs, longtable, rotating, lscape}

\DeclareGraphicsExtensions{.jpg, .eps, .png}


\usepackage{enumerate,latexsym,amsmath,amssymb, amsthm, algorithm, algorithmic, verbatim}

\usepackage{listings}
\usepackage{color}

% Use of & in the acronyms
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}



%%%%%%%%%%%%%%
%% Acronyms %%
%%%%%%%%%%%%%%
\usepackage[printonlyused,withpage]{acronym} 

\newcommand{\listofacronymsname}{Acronyms}

\newcommand{\listofacronyms}{%
\chapter*{\listofacronymsname}%
\addcontentsline{toc}{chapter}{\listofacronymsname}%
\label{sec:acronyms}%
\markboth{\listofacronymsname}{\listofacronymsname}%
}


\usepackage[authoryear,round, nonamebreak]{natbib}

% Reference which pages the citation was referenced in
\usepackage[pagebackref, breaklinks]{hyperref} 
\renewcommand*{\backref}[1]{[pp. #1]}

Can anyone think of any reason why this error might be coming up? I'm really stumped here. Please let me know if you need any more information. I know this is a bit skim, but the thesis is quite large at this point and I'm not sure what would be of help or not.

Cheers, Christos