> What's interesting to me is that it works in the Squeakland image 
> (which is derived from 3.2), with the same VM.
> 
> So I'm a bit puzzled as to what may have changed since then.

Depends on what you mean by "it" works ;-) The problem I've been describing
has been around for as long as Squeak but it depends a bit on the
environmental factors. In this particular case it is probably
SketchMorph>>drawOn:.

Cheers,
  - Andreas