par in embedded Metapost not accepted

["Johannes Hüsing" <tmi0m0@spi.power.uni-essen.de>]

Dear contextuals,

The included file runs smoothly when processed with Metapost. When I 
embed it into a ConTeXt file with \startuniqueMPgraphic, \stop..., 
\uniqueMPgraphic, I get the following error message:

Runaway argument?
{ def ptc(expr radius, angle) = (radius*cosd(angle), radius*sind(angl\ETC.
! Paragraph ended before \handleuniqueMPgraphic was complete.
<to be read again> 
                   \par 
\MP:zahnrad ..., radius*sind(angle)) enddef; \par 
                                                  def zahnrad(expr r, dr, dw...

\douniqueMPgraphic ...es [#1][#2]\getvalue {MP:#1}
                                                  {}}
<to be read again> 
                   }
l.227 einen anderen}{\uniqueMPgraphic{zahnrad}}

?

I am calling \uniquegraphic as an argument to \placefigure here. What am
I doing wrong?

Thanks for any input

Johannes