This error is the most common reason that automatic imports do not work.
The short explanation is: you have two options. You can either contact your web host and ask them to increase the MySQL buffer length or max packet size (it’s okay if that doesn’t mean anything to you – the tech support folks at your web host will understand), or you need to do a manual import.
Here is the longer explanation: Every time you make a change to the database of your staging site, WP Stagecoach keeps a record of what change you made. Then, when it is time to do the import, it tries to make every single database change on your live site as well. (In other words, instead of just copying over your database, it actually goes through the database and does everything you did, one step at a time.) If you make a lot of database changes on your site, and if your web host has a relatively low MySQL buffer length or packet size, then you will run into this error. That is why you need to ask your web host to change the buffer length and/or packet size.