While the error
can actually be caused by offering the package a figure which claims to have a zero dimension, it's more commonly caused by rotation.! Package graphics Error: Division by 0.
Objects in TeX may have both height (the height above the baseline) and depth (the distance the object goes below the baseline). If you rotate an object by 180 degrees, you convert its height into depth, and vice versa; if the object started with zero depth, you've converted it to a zero-height object.
Suppose you're including your graphic with a command like:
\includegraphics[angle=180,height=5cm]{myfig.eps}
In the case that myfig.eps has no depth to start with, the
scaling calculations will produce the division-by-zero error.
Fortunately, the graphicx package has a keyword
totalheight, which allows you to specify the size of the
image relative to the sum of the object's height and
depth, so
\includegraphics[angle=180,totalheight=5cm]{myfig.eps}
will resolve the error, and will behave as you might hope.
If you're using the simpler graphics package, use the
* form of the \resizebox command to specify the use of
totalheight:
\resizebox*{!}{5cm}{%
\rotatebox{180}{%
\includegraphics{myfig.eps}%
}%
}
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=divzero