TeX capacity difficulty

Good afternoon all from Greg Bennett
running MiKTeX 2.9 Version 3.1415926-2.3.1.40.12 (preloaded format = 
latex 2011.6.26)
inside WinEdt6 (Build: 20110315 (v.6.0)
under Windows7 Pro, 64bit

I post to this newsgroup since it is MiKTeX which is my TeX engine. 
Apologies if I should have
posted to, eg., comp.text.tex straight away.

I have been tidying up the files from which a large book is compiled 
under amsbook. The
entire project does compile.

In the directory BOOK, there is a book-things.tex file which holds 
definitions in the form of
\newcommand instructions.

Several of the BOOK/CHn directories have their own CHn-things.tex files, 
as is the way with
a project with two authors, and with material some of which is quite 
specialised.

Some of these CHn-things.tex files have a mixture of \newcommand  and 
\def forms.

I began by copying all the definitions from CHn-things.tex -> 
book-things.tex, excluding the loading of
the CHn-things.tex files, and recompiling the entire project - successfully.

They I started to convert the \def forms to \newcommand forms, checking 
for complete compilation
every now and then, and having always thought of \newcommand as a 
wrapper for \def and relatives.

Unfortunately, I reached a point at which the conversion of just one 
additional \def and starting the
compilation led, part way through,  to
  TeX capacity exceeded [grouping levels = 255] sorry
the difficulty which we all dread.

I do not know how to proceed, either with what additional information I 
should accumulate, or where
I should pursue this matter.

Thanks in advance for any and all assistance
Cheers
/Greg Bennett




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