Hi William,
A quick update on this investigation:
We've discovered that Mac OS 10.8+ fails to handle low-memory conditions when it only has a single processor core available to it. The exact same failure occurs on a physical Mac configured to use only one processor core and limited RAM, so it is not a virtualization-specific problem. We'll continue to investigate it here and see what we can do about it.
In the meantime, allocating at least two processor cores to your VM should make the problem go away.
Cheers,
--
Darius