Thank you, that's very helpful. I can picture what's going on somewhat better now. I'm going to have to break down and boot the VM, aren't i?
ETA - I looked at the files with mobi2mobi gui, and the AISN had been changed. I tried another few books and it was working, but there are a couple of books that simply won't work.
Syncing isn't terribly important to me, I almost always have my Kindle with me, but I'm stubborn and want to figure this out
Thanks for the pointers.