On 21 Jul 2016, at 19:21 , : Hans Hagen <pragma@wxs.nl> wrote>

On 7/21/2016 3:53 PM, Robert Blackstone wrote:

One my project files, that In previous versions of the standalone mkiv compiled without any problems, doesn't compile in the standalone I installed recently (version 2016.07.18 16;26).
It gives me an error warning hat I don’t understand:
+++++++++++++++++
tex error       > tex error on line 191 in file TD-Ch0-R1-index-UTF8-4CUP.tex: ! Missing number, treated as zero

......
l.191 \stopintro
+++++++++++++++++

The processed file starts with:
++++++++++++++++++
\definehead     [intro] [chapter]
\setuphead      [intro] [number=no,alternative=middle,style=\tfa \bf]

\startcomponent TD_Ch0-Intro.tex
\intro[bookmark=,label=,list={Introduction},marking=,reference=ch:Intro,title={Introduction}]

shouldn't that be \startintro then?

Yes. 
Problem solved. Thank you.
(It has been nice that the previous versions have been very forgiving for a fool like me.)

Best regards,
Robert