Metapost stopped working

Hi all,

I installed MiKTeX on three different machines running under Windows 10 
and I have a serious problem concerning MetaPost in two of them. 
Whenever I try to compile any MetaPost file containing text, such as 
this one:

-------------------- test.tex --------------------
prologues := 0
beginfig(1)
   label(btex a etex,(0,0));
endfig;
end
--------------------------------------------------

a window pops up saying that MetaPost has stopped working. Any idea 
about what I should do?

Best regards,

José Carlos Santos

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