I do my local development using xampp without SSL and don't have an issue using the "Place Order" button from one of my test installations. Are you sure that your admin's /includes/configure.php file doesn't indicate that your store-front uses SSL? If you're not using SSL, then your admin's configure.php file should look similar to:
Code:
/**
* WE RECOMMEND THAT YOU USE SSL PROTECTION FOR YOUR ENTIRE ADMIN:
* To do that, make sure you use a "https:" URL for BOTH the HTTP_SERVER and HTTPS_SERVER entries:
*/
define('HTTP_SERVER', 'http://www.example.com');
define('HTTPS_SERVER', 'https://www.example.com');
define('HTTP_CATALOG_SERVER', 'http://www.example.com');
define('HTTPS_CATALOG_SERVER', 'https://www.example.com');
// secure webserver for admin? Valid choices are 'true' or 'false' (including quotes).
define('ENABLE_SSL_ADMIN', 'false');
// secure webserver for storefront? Valid choices are 'true' or 'false' (including quotes).
define('ENABLE_SSL_CATALOG', 'false');