[GRiker]

@chilady1,
Is the error you're reporting occurring consistently? If so, please create a GitHub issue with a debug log.

There have been a few instances of crashes similar to the one you report filed at the GitHub issue tracking site. I have not been able to pinpoint the source of the problem, nor replicate it on any of my iDevices. Here are the steps that have been found to work for most of the people initially reporting similar problems. Each of these steps should be tried individually.

1. Update to the most recent version of iTunes. If you have iOS7 on your iDevice, you need iTunes 11.1 or later.
2. Update to the most recent version of calibre.
3. Exit calibre. Disconnect the iDevice. Restart the computer. Reconnect the iDevice. Restart calibre.
4. Exit calibre. With the iDevice connected, start iTunes, confirming that your iDevice is shown as a connected device. With iTunes running, start calibre.
5. Exit calibre, disconnect the iDevice. Do a hard reset on the iDevice by pressing and holding the Home and Power buttons until the iDevice shuts off and you then see the Apple logo, then release the buttons. Reconnect the iDevice! restart calibre.
6. Reinstall iTunes on your computer.
7. Create a backup of your iDevice using iCloud or iTunes! then restore the installation of iOS7 on your iDevice.

Please report back if one of these steps resolves the problem for you.

G