My best guess is that you didn't upload all of the necessary files to the remote server. Make sure to upload the entire webassist/ecart folder. If that doesn't work I'll need FTP information to debug it.
You can try adding:
<?php
ini_set('display_errors',1);
?>
if that is on the top of the page it might display an error instead of a blank page that might give you something more to go on.