The most common reason for the "MySQL server has gone away" error is that the web server timed out and closed the database connection prematurely, which is often due, except in rare cases, to a lack of resources on the server.
This is not a Wordpress Magic error. We recommend that you contact your hosting provider in this regard.
You can also try to optimize your Wordpress database, or disable other plugins whilst Magic Content Wizard is running (you'll need to work out which plugins you need to disable to make it work best for you.) The key is to try and minimise the load on the server.
If you're a little code-savvy (or are feeling brave), two possible workaround's which may work for you (NOT SUPPORTED) are:
Download the wp-db.php replacement file on this page and follow the installation instructions as ountlined there, OR
Add the following code at line number 334 in wp-includes/wp-db.php file: $this->query("set session wait_timeout=600");