boolean probleme

Hi, I do not understand, I just finished to activate and adjust CFWC and I each, i had this message on my form :

“Warning: Illegal string offset ‘boolean’ in /xx/xx/www/home/wp-content/plugins/contact-form-with-captcha/cfwc-main.php on line 250”

thank you in advance for your help

http://wordpress.org/plugins/contact-form-with-captcha/