I had another random thought on the subject.  My iPods work, but they
don't display a geometry message (though flash disks do), and do display a
'not ready' message.  The failing ones don't say "not ready", but do
display a bogus geometry.  This sounds to me like a race condition, though
I'm not certain of what type.

It could be that the new iPod is a bit later on the "not ready" status, so
it's not caught immediately; however, the device isn't ready when the
geometry is probed, so it gives bad answers.  Or maybe it's buggy and
isn't saying "not ready", though it should, because it can't give status
yet.

It would be interesting to insert a 1- or 2-second delay call before the
device is queried for geometry.