Blossom or SamL (Or anyone using Fire with Calibre), I wonder if you might take a minute to confirm something that will potentially help Kovid. I noticed that (after updating and using calibre to send a book to my Fire) a second connection AFTER sending a book, does not result in calibre detecting the book(s) I sent to the device on the first connection. So if you wanted to try that, then post your findings here:
It might help to get this resolved. Or, at least, tell me that the problem is my end.