This problem got me for a few hours the other day and google was barely helpful. So I thought I'd share this.
When you write a custom validator, you have to tell the form object where to look. I was unable to find a way for the autoloader to find it (please correct me if there is!). I'm not a fan of this syntax because I don't like burying and hard coding path information this deep into the code, especially with a framework as configurable as Zend.
