Do you have installed firebug? Submit the form and keep an eye on firebug console. You'll get an ajax response back. Normally this is a JSON response, but in your case this should be malformed. Let me know.
<b>Warning</b>: DOMDocument::loadHTML(): Empty string supplied as input in <b>X:\Softwares\Internet\Xampp\htdocs\wp-content\plugins\wp-user-frontend-pro\class\frontend-form-post.php</b> on line <b>295</b><br />