problem with m-ch-en (Context macro)

Hi Folks:

I am a new and rather naive user.  I have been using latex for  
creating documents with chemical equations, with preamble entries  
such as

\usepackage {chemarr}
\usepackage {m-pictex}
\usepackage {m-ch-en}


After upgrading to 3.0, I now have the following error:

% latex finalexam.tex
This is pdfeTeX, Version 3.141592-1.21a-2.2 (Web2C 7.5.4)
entering extended mode
(./finalexam.tex
LaTeX2e <2003/12/01>
<snip>
(/sw/share/texmf-dist/tex/latex/context/m-pictex.sty
(/sw/share/texmf-dist/tex/context/base/m-pictex.tex
(/sw/share/texmf-dist/tex/generic/pictex/prepictex.tex)
(/sw/share/texmf-dist/tex/generic/pictex/pictex.tex)
(/sw/share/texmf-dist/tex/generic/pictex/postpictex.tex)))
(/sw/share/texmf-dist/tex/latex/context/m-ch-en.sty
(/sw/share/texmf-dist/tex/generic/context/m-ch-en.tex
(/sw/share/texmf-dist/tex/generic/context/ppchtex.noc
(/sw/share/texmf-dist/tex/context/base/supp-mis.tex
loading : Context Support Macros / Miscellaneous (2004.10.26)
! No room for a new \dimen .
\ch@ck ...\else \errmessage {No room for a new #3}
                                                   \fi
l.197 ...\nextdepth      \do \newdimen  \nextdepth


Any suggestions how to make it work?

I am using os x v. 10.4.1, and have tried multiple different latex  
installations, all of which give the error.  It used to work fine  
using latex 2.0.x installed via fink; no other version of 2 or 3 has  
worked for me.

Thanks in advance for help and advice.

Bill