When you change the DNS and it propogates, are you able to go directly to the upgrade script and run it? Are you able to upload a simple php page, or html page, to the new server and view it without error (after the DNS propogation)?
Simple php script here - http://php.net/manual/en/tutorial.firstpage.php
Simple php script here - http://php.net/manual/en/tutorial.firstpage.php
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