MM Forms Line 60 Captcha Error – Could Not Read Font

I am trying to use the Captcha function of MM forms and I get the following error:

Warning: imagettftext() [function.imagettftext]: Could not read font in /homepages/15/d211799029/htdocs/DEVILSCANYONBREWERY/wp-content/plugins/mm-forms/captcha/captcha.php on line 60

http://www.devilscanyonbrewery.com/bop/