LaTeX Graphicx Package Troubles

I’m authoring my thesis in LaTeX, a sort of scripting language similar to HTML that produces beautiful final results… that is, if you can get it to cooperate.

My current problem is with trying to use the graphicx package.  I can’t get a graphic to display correctly.  The code looks correct but it keeps throwing strange errors.  I copied the code verbatim (with changing the file i’m trying to insert) from a friend’s masters thesis.  It worked in his so I don’t see why it’s not working in mine.  We are using the same class files and whatnot and the same general format.

The problem comes (i think) in the width variable.  That textwidth doesn’t seem to be working correctly.

The Code:

\begin{figure}[h]
\begin{center}
\includegraphics[width=0.6\textwidth, keepaspectratio=true ]{figures/hofstede_onion.png}
\caption{Hofstede's Onion Model of Culture: Cultural Values are located at the core and are surrounded by Rituals, Heros, and Symbols with Practices drilling down from the outside to the Values center. Reproduced from \cite{Hofstede01}.}
\label{fig:hofstede_onion}
\end{center}
\end{figure}

The Error Message:

! LaTeX Error: Cannot determine size of graphic in figures/hofstede_onion.png (no BoundingBox).
See the LaTeX manual or LaTeX Companion for explanation.
Type H for immediate help.
...
1.18 ... ctratio=true ]{figures/hofstede_onion.png}
) [5]

Thoughts, insights, ideas?

UPDATE:

With the help of Alex (recommended by Anne), I was able to get the graphics files to pop out.  The key was switching from outputting into a DVI file or a PS file to outputting directly into a PDF file.  To do this in TeXnic Center, I went to Build -> Select Output File.  I then chose the PDF option.

Other problems still exist with my output, but at least some of the big ones are now addressed.  No doubt, there will be further whining for help as I progress with my thesis.