Alan,

> Since SUnit tests seems to corrupt my image, I've been using a seperate 
> instance for testing VMs.
> 
> I've found that, on occasion, it will fail fairly badly, then uppon 
> quitting/nosave and re-trying (exact same sequence of commands) it would 
> perform brilliantly!

  You're testing your modified VM, right?

> Furthermore there seem to be two classes of errors, one will happen with 
> a frequency of roughly 25% while another fails 80% of the time but 
> succedes on the other 20%.
> 
> =\
> 
> This screams "race condition" to me....

  It could be that your memcpy equivalent is wrong?  For example, if
the compaction phase, or any phase, of the garbage collection, is not
doing correct thing, or object creation doesn't do nil-out, etc.,
etc. can cause this kind of errors.

-- Yoshiki