it also gets stuck here

["Denis B. Roegel" <Denis.Roegel@loria.fr>]

The example below also gets stuck if I uncomment the 
\setupbodyfont line.

Denis

\setupcolors[state=start]
\starttext
\startMPenvironment
%\setupbodyfont[loc,mt,ppl,pcr,10pt]
\definefont[RotFont][RegularBold]
\stopMPenvironment

\resetMPdrawing
\startMPdrawing
  picture pic[];
  numeric wid[], len[], pos[], n;
  wid[0] := len[0] := pos[0] := n := 0;
\stopMPdrawing

\def\whatever#1%
  {\appendtoks#1\to\MPtoks
   \setbox\MPbox=\hbox{\bfd\the\MPtoks}%

\startMPdrawing
  n:=n+1; len[n] := \the\wd\MPbox;
\stopMPdrawing

\startMPdrawing[-]
  pic[n] := btex \bfd#1 etex;
\stopMPdrawing}

\handletokens MetaPost is Fun!\with\whatever

\startMPdrawing
  pair len; len := origin;
  for i=1 upto n:
    draw pic[i] shifted len;
    draw boundingbox pic[i] shifted len
      withpen pencircle scaled .25pt withcolor red;
    len:=len+(xpart lrcorner pic[i]-xpart llcorner pic[i],0);
  endfor;
\stopMPdrawing

\MPdrawingdonetrue
\getMPdrawing

\stoptext