I emailed customer service on ereader.com (makers of DropBook) right before posting here - i.e. days ago - and no one answered.
My understanding is that DropBook handles more PML than eBook Studio - or so says the readme. DropBook is a more mature program. eBook Studio just has a WYSIWIG interface so you don't have to write PML.
My rep at Ingram is no help at all with this (so far - trying to stay optimistic). I don't know what to do.