FYI- For those using a cloud backup for Calibre...
If you have your Calibre library folder set to be continuosly synched to the cloud (ie: Library folder is in your Dropbox folder, or you have a shortcut link to your Library folder in your Copy folder), Kovid
STRONGLY recommends that you
pause synching while you are using Calibre. Synching while you are using Calibre falls under the category of having the Library folder being accessed by two programs at the same time which is a big no-no. I personally was very aware of the prohibition against two users accessing the Library folder at the same time, but did not realize that an upward synch to the cloud was looked at the same way.
If you want to read the thread it is
here...