Hyperref Doesn't link \cite Command

It has been 2 years since this question was asked, but I will write my solution because I had the same problem.

As suggested by many, hyperref should be imported last. I also tried that but failed to hyperlink my citations in the document. So, the problem is with the ieeeconf.cls. If you open it with the latex editor you are using you'll see the following:

% 2) Provide a fake nabib command \NAT@parse so that hyperref will not
%    interfere with the operation of cite.sty. However, as a result citation
%    numbers will not be hyperlinked. Also, natbib will not be able to work
%    with IEEEtran. However, this is perhaps the best solution until cite.sty
%    and hyperref.sty are able to co-exist with each other.
%    It easy enough to override the fake command via:
%    \makeatletter
%    \let\NAT@parse\undefined
%    \makeatother

Here is my example:

\documentclass[letterpaper, 10 pt, conference]{ieeeconf} 
\IEEEoverridecommandlockouts                              
\overrideIEEEmargins                                     % Needed to meet printer requirements.

\usepackage{times}                                       % assumes new font selection scheme installed
\usepackage{amsmath}                                    %assumes amsmath package installed
\usepackage{amssymb}                                     % assumes amsmath 
\usepackage[export]{adjustbox}
\usepackage{footnote}

\makeatletter
\let\NAT@parse\undefined
\makeatother
\usepackage{hyperref}  %hyperref still needs to be put at the end!

\title{\LARGE \bf
Some Title*
}

\author{Author One$^{1}$, Author Two$^{2}$    % <-this % stops a space
\begin{document}
   \maketitle
\thispagestyle{empty}
\pagestyle{empty}

\begin{abstract}
 Some Random Abstract.
\end{abstract}

\section{Introduction}

 Results from the \cite{a}, \cite{b}, \cite{c} serve as motivation...

\begin{thebibliography}
\bibitem{a} First reference
\bibitem{b} Second reference
\bibitem{c} Third reference

\end{thebibliography}

\end{document}  

I just included the three lines suggested in the cls file. As Schweinebacke remarked, this is for the old version of ieeeconf.cls.

Your code contain several errors. In my MWE below I corrected them. The main errors are marked with <============.

Some remarks:

• The hyperref has to be (except in rare cases) the last package in the preamble.
• Your command \begin{thebibliography} is not correct. It has to has a length parameter for the labels like \begin{thebibliography}{99}.
• The \bf is outdated. Use \textbf{...} instead or \bfseries.
• I commented your two IEEE commands, they are unknown in the class I have.
• Your command \author{} was not closed with a }.
• Define block element is not needed for the MWE (BTW: Why do you use it?)
• Preamble of your MWE contain several packages (amsmath, footnote, ...) not used in your code. Since they are not related to the your problem, you can omit them!

MWE:

\documentclass[letterpaper, 10 pt, conference]{ieeeconf} % IEEEconf
%\IEEEoverridecommandlockouts                              
%\overrideIEEEmargins     % Needed to meet printer requirements.

\usepackage{times}    % assumes new font selection scheme installed
\usepackage{amsmath}  % assumes amsmath package installed
\usepackage{amssymb}  % assumes amsmath 

\usepackage{xcolor} % <======================================= for green
\usepackage[export]{adjustbox}
\usepackage{footnote}

\usepackage{hyperref} % <====================== last packge to be called
\hypersetup{linkbordercolor=green}

\title{\LARGE 
\textbf{Some Title}*
 }

\author{Author One$^{1}$, Author 2$^{2}$} % <================= missing }

\begin{document}
\long\def\/*#1*/{}                              % Define block comment

\graphicspath{ {Chart and Figures/} }

\maketitle
\thispagestyle{empty}
\pagestyle{empty}

\begin{abstract}
Some Random Abstract.

{\textit{Index Terms}~-- Life Science and Health Care; Mechatronics; 
Emerging      Topics in Automation}
\end{abstract}

\section{Introduction}

Results from the clinical studies \cite{cervino, c2, c3} serve as 
motivation   for minimizing patient positioning errors during IGRT in 
order to minimize   positioning-related uncertainties in cancer dose 
treatments, improve tumor   control, and reduce toxicity \cite{c4, c5}.

\begin{thebibliography}{99} % <==================== length missing! {99}
\bibitem{cervino} Cervino, L.I., Pawlicki, T., Lawson, J.D., Jiang, S.B., Frame-less and mask-less cranial stereotactic radiosurgery: a feasibility study. Phys. Med. Biol. 55 (2010) 1863-1873.
\bibitem{c2} Xing, L., Dosimetric effects of patient displacement and  collimator and gantry angle misalignment on intensity modulated radiation  therapy. Radiother Oncol, 2000. 56(1): p. 97-108.
\bibitem{c3} Manning, M.A., et al., The effect of setup uncertainty on normal tissue sparing with IMRT for head-and-neck cancer. Int J Radiat Oncol Biol Phys, 2001. 51(5): p. 1400-9.
\bibitem{c4} Hong, T.S., et al., The impact of daily setup variations on head-and-neck intensity-modulated radiation therapy. Int J Radiat Oncol Biol Phys, 2005. 61(3): p. 779-88.
\bibitem{c5} Den, R.B., et al., Daily image guidance with cone-beam computed tomography for head-and-neck cancer intensity-modulated radiotherapy: a prospective study. Int J Radiat Oncol Biol Phys, 2010. 76(5): p. 1353-9.

\end{thebibliography}

\end{document}

and the result:

I would suggest to use biblatex with a bib file.