Comment 2 for bug 1198248

From memory, the last time I saw the first error, it was because of a book with an unusual character in its name. But, anything that calibre has sent to the device should have an OK name. Have you manually sideloaded something since the last time you used calibre?

The second makes me think the connection to the Mini has been lost. That could be the cause for the first error, but is more likely a side effect.

Can you do some checks?

Firstly, connect the Mini without calibre running. Then check you can see the drive for the device and copy a file to it. It doesn't matter what you copy, it is just to make sure Windows is seeing the device properly.

Secondly, without the Mini connected, start calibre and the restart in debug mode. This is done by right clicking on the preferences button and selecting "Restart in debug mode". Calibre will restart and display a message about a log file. Then connect the Mini and wait for the initial sync jobs to finish. Or the error you see above. Then close calibre. The debug log will be opened in Notepad. Post the full contents of the log.