you say this started happening after making a small update to the form? but it was working before? what was the small update?
it could be that there is a php error occurring, try adding the following code to line 1 of the form page to turn error reporting on, once we know the error, we can tell where to begin troubleshooting:
<?php
error_reporting(E_ALL);
ini_set('display_errors','on');
?>