Are you really (really?) running Zen Cart v1.2.x? If so, that might explain your issue as more and more webhosts are no longer supporting the more ancient versions of PHP (like PHP 5.2.17).

You can determine your currently-installed Zen Cart version by inspecting the file /includes/version.php. That inspection can be performed either using an FTP program (like FileZilla) or your webhost's cPanel to inspect your store's file system.