I've seen that a couple times. The SQLite DB got corrupted. I haven't quite found the source of what can cause it other than the T1 sometimes not going into Data Transfer Mode correctly when you tell it to, and instead going to the home screen. SQLite doesn't always like two processes trying to edit the DB at the same time.
You can delete books.db, and let the T1 recreate it. Or you can try to repair the SQLite DB yourself. You will need SQLite 3 tools installed on your machine to do it.
On a Mac, you would run this from the terminal:
Code:
echo ".dump" | sqlite3 old.db | sqlite3 new.db
Where old.db is the path to 'books.db' and new.db is a place to put the new books.db. You can replace the books.db on the device with the new one.