\startMPenvironment : personal font weirdness

[David Wooten <dw@trichotomic.net>]

Greetings all,

I've been experimenting with MetaPost/Fun of late. It is indeed fun. In 
trying to have a uniform font in both text and MP areas, however, I am 
running into some difficulty. With a little file like this:

---

\setupcolors[state=start]
\setuppagenumbering[state=stop]

\startMPenvironment [global]
    \usetypescript[palatino][ec]
    \switchtobodyfont[palatino,12pt]
\stopMPenvironment

\starttext

The following example should be very interesting:
\blank

\startuseMPgraphic{very-interesting}

z40 = (2cm,0cm)    ;     z41 = (3cm,0cm) ;
z42 = (3cm,1cm)    ;     z43 = (2cm,1cm) ;
z46 = (2.5cm,.5cm) ;

path F ; F := (z40--z41--z42--z43--cycle) ;

linejoin := mitered ;

drawpath F ;
label("very", z46) ;

\stopuseMPgraphic

\useMPgraphic{very-interesting}

\stoptext

---

everything works very nicely (fonts identical). When I use my own 
typescript file, however:

---

\startMPenvironment [global]
    \usetypescriptfile[minionpro-diss]
    \usetypescript[Minion]
    \switchtobodyfont[Minion,12pt]   
\stopMPenvironment

---

The text appears in the correct font, but the MP section, _while at 
first showing the correct font_, then changes to CM before my eyes. (my 
pdf viewer auto-updates).

Any clues?

Many thanks,
David