[paulrw]

Is this the correct place for this?
Yesterday I set up a new library and imported 60ish books to it, edited metadata, covers etc. converted to ePub, and checked all was well. Restarted my PC for updates and the library had disappeared completely - can't find it on disc (I didn't actually check that Calibre had put it where I thought I had told it to when I was working on it), and now when I click the Library icon I get

ERROR: ERROR: Unhandled exception: <b>ImportError</b>:Bad magic number in C:\Program Files\Calibre2\Lib\site-packages\calibre\gui2\dialogs\choose_library_ui.py o

Traceback (most recent call last):
File "site-packages\calibre\gui2\layout.py", line 420, in choose_library
File "site-packages\calibre\gui2\dialogs\choose_library.py", line 12, in <module>
ImportError: Bad magic number in C:\Program Files\Calibre2\Lib\site-packages\calibre\gui2\dialogs\choose_library_ui.py o

Following my previous experience I have checked the wastebasket in case Calibre had arbitrarily decided to to delete the folder, but it is not there.
I Love Calibre's functionality, but am slightly frightened by how easily it seems to lose books. I also had an experience yesterday where my library (before creation of second library) was showing 534 books, I added another 20 and it showed 515! I haven't yet tracked down whether that is genuine or not - one of the main reasons for Calibre is that I have ebooks in a lot of different places so it is not easy to check the Calibre library against the original sources.
One thing I have noticed is that there are quite a lot of duplicate folders for authors, one of which is always empty. If I could get the library function working again I was thinking of creating a new library and importing from the folder structure of the old one to clean it up - would this be sensible?