after Kindle firmware update, all my books are gone!

Hello all,

I'm desperate for help. I have the cheapest kindle, the $60, 3rd gen I believe, and today it automatically updated. I had on it a bunch of books from gutenberg.org.

It simply won't recognise them. I have removed it all, and added it again with Calibre. Nothing, it`s like their not on the device, but in Calibre, I can see them there.

Anyone has any idea what`s going on and how to fix it?

Thanks!