In the following example, it is the ";" that leads to the error
\def\vect#1{%
  \overrightarrow{#1}
}
\starttext
$({\rm O};\vect{e_{x}})$
\stoptext

If you suppress it, it works fine. (???)

2009/5/13 Aditya Mahajan <adityam@umich.edu>

> On Wed, 13 May 2009, Flavien Lambert wrote:
>
>  Dear all, I didn't use ConTeXt for some time and, so, have just
>> re-installed
>> the minimals tonight. When running on some of my files, Mark II does its
>> job
>> well but Mark IV tells me
>>
>> error: Invalid field id nucleus for node type choice (0)
>> .
>> l.133 ... M décrit l'axe $({\rm O};\vect{e_{x}})$
>>                                                  avec une vitesse
>> $\dot{x}...
>>
>> I have absolutely no idea what it is trying to say to me...
>> If related, the macro is defined by
>> \def\vect#1{%
>>  \overrightarrow{#1}
>> }
>>
>
> Can you create a minimum example. This runs fine here
>
> \def\vect#1{%
>  \overrightarrow{#1}}
>
> \starttext
> $\vect{e_{x}}$
> \stoptext
>
> Using ConTeXt  ver: 2009.05.12 22:35 MKIV
>
> Aditya
>
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-- 
Flavien.
----------------------------
"Quantum objects are completely crazy but, at least, they are all crazy in
the same way." R.P. Feynman.