[l2h] Where is \voidb@x supposed to be defined?

[Julius Smith]

Does anyone know where the macro \voidb@x is supposed to be 
defined?  LaTeXtoHTML expects it to be defined, but it is not defined in my 
environment.  Am I missing some package?

In images.tex, I have
...
\newcommand\lthtmlboxmathZ{\@next\next\@currlist{}{\def\next{\voidb@x}}%
...
{\newpage\clearpage
\lthtmlinlinemathA{tex2html_wrap_inline20900}%
$ \unhbox \voidb@x \hbox {{\sc  Repeat}}_3(X)$%
\lthtmlinlinemathZ
\lthtmlcheckvsize\clearpage}

In images.log, I see
...
l2hSize :tex2html_wrap_inline20880:8.7125pt::8.7125pt::23.74532pt.
[34


]
! Undefined control sequence.
l.1049 $ \unhbox \voidb
                        @x \hbox {{\sc  Repeat}}_3(X)$%
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

! Missing number, treated as zero.
<to be read again>
                    @
l.1049 $ \unhbox \voidb@
                         x \hbox {{\sc  Repeat}}_3(X)$%
A number should have been here; I inserted `0'.
(If you can't figure out why I needed to see a number,
look up `weird error' in the index to The TeXbook.)

---------------------

Also, it is not clear to me how the images are ordered in images.tex.
They do not seem to be arranged in order of occurrence in the source.
As a result, I don't know how to find the original offending formula
in order to try various work-arounds.

Thanks for any ideas,
Julius