Standard import/export will not work when data is based on any type of ID value (post ID including images, term ID, user ID, etc).
When moving a site I generally duplicate the entire database. I use phpMyAdmin to export the DB from the site and then import it into the new DB. Then I use a tool found here https://interconnectit.com/products/search-and-replace-for-wordpress-databases/ to make any DB changes that are needed (alter domain name if needed).
This can also be accomplished with some site backup and restore plugins.
