|Just to let you know, I needed to use this :|
From here: http://us2.php.net/imagettftext
"In many cases where a font resides in the same directory as the script using it the following trick will alleviate any include problems.
// Set the enviroment variable for GD
putenv('GDFONTPATH=' . realpath('.'));
// Name the font to be used (note the lack of the .ttf extension)
$font = 'SomeFont';
In the function MakeCaptcha () of captcha.class.php.
I just put that in, and changed "$this->Font" to "$font"