CDbCommand failed to execute the SQL statement
A 2006: MySQL server has gone away error generally means that (for any number of reasons) the connection between Craft/PHP and the MySQL server has been dropped.

Common causes are from connection timeouts and misconfigured MySQL settings like max_packet_size.

There are lots of debugging tips in the above link from MySQL's official documentation that would be a good place to start.  Additionally you might want to involve your host and let them know what you're seeing.