eps graphics cause intermittent missing characters

When displaying a prosper-produced PDF file in Windows Acrobat Reader,
everything is usually fine until I get to a slide with a graphic that
I've included as an eps or ps file with \includegraphics.  Then
sometimes, but not always, there are missing characters, but only in the
title of the slide, not anywhere else.  Once this happens, every slide
has missing characters in the title, unless I back up in acroreader
until the first slide, and then go forward again.  The first slide is
always fine, and when I go forward again, I don't get the problem again
until I reload the file in acroread.

Sometimes the first instance of the problem is accompanied by an
Acroreader error such as: "Could not find the XObject named 'R176'."

Any ideas about what's going on?  Even if there's not a full-fledged fix
for the problem, if I understood it and could be sure that going forward
through the whole presentation and then back to the beginning again
would always get rid of the problem, that would be enough.  Then I'd
just have to remember to do that before beginning a presentation.

Thanks in advance for any suggestions or advice-

Marshall


Further details in case they matter:

I'm using PPRdefault.sty or a slightly modified style I named
"PPRblank.sty".  The problem occurs either way.  The problem occurs both
with Windows Acrobat Reader 7.0 and 5.0.  (In xpdf 3.01 under Cygwin I
get dropped characters and missing XObject messages right away as soon
as I'm past the first slide.)  I'm using prosper 1.24 under Cygwin in
Windows XP with teTeX 3.0.0-3 .  (That is, I'm running LaTeX in Cygwin's
Unix emulation under Windows, but the Acrobat Reader is just a native
Windows version.)

The eps files are made using xfig and its associated translation
utilities, or with metapost (derived from metafont).  At first I thought
the problem had to do with the metapost-generated files, which have
caused me difficulties with fonts over the years, but I got the problem
even with the xfig-generated eps files after I took out the
metapost-generated files.

This is the relevant part of my LaTeX preamble:
\documentclass[%
pdf,
%ps,
nocolorBG,
%colorBG,
%slideColor,
slideBW,
noFooter,
final,
blank  % added by Marshall
]{prosper}

\usepackage{natbib}
\usepackage{xspace}
\usepackage{epsfig}
\usepackage{graphics}



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