Copying wordpress to another server breaks it on original server

If you didn’t hand-change the wpurl in the dev database, what probably happened is that you entered your url, and WP made a 301 redirect to the live site. Then, without realizing it, you changed the url config in your live site.

To make it work:

Put this in your wp-config.php

define('WP_SITEURL', 'http://your-wp-url.com');
define('WP_HOME', 'http://your-wp-url.com'); 

That should do it.