Dear Chaley,
Recently, as I noticed, when Calibre library is updated in Box.net, CC only shows "Checking database..." message and then without the "Downloading....%", the updated library is opened (yes, it seems only the download process was not displayed, but often it made me think that the connection was lost). With Dropbox, the Download progress message appears.
Recently, as I noticed, when Calibre library is updated in Box.net, CC only shows "Checking database..." message and then without the "Downloading....%", the updated library is opened (yes, it seems only the download process was not displayed, but often it made me think that the connection was lost). With Dropbox, the Download progress message appears.