Help With the Check Function

Thanks for creating the Really Simple Captcha. I am using the plugin to integrate captcha on a custom contact form in WordPress. I have read and followed the instructions and the one tutorial I found on the net: http://www.lost-in-code.com/platforms/wordpress/wordpress-plugins/wordpress-using-really-simple-captcha/

So my contact form breaks on the check function.

My form displays the captcha, the files are getting created and saved in the tmp folder successfully. When the form submits it breaks at the check function. here is my simple POST code:

if($_POST['contact_form'])
                {
                    $captcha_prefix = $_POST['captcha_prefix'];
                    $captcha_code = $_POST['captcha_code'];

                    echo $captcha_prefix;
                    echo '<br/>';
                    echo $captcha_code;

                    $correct = $captcha_instance->check( $captcha_prefix, $captcha_code );
                    echo '<br/>';
                    echo $correct;

]

on submission, my values are getting passed and displayed. then the page breaks at this line:
$correct = $captcha_instance->check( $captcha_prefix, $captcha_code );

Any help would be greatly appreciated.

Thanks,

Darren

https://wordpress.org/plugins/really-simple-captcha/