DidrikBirkemalm on "[Plugin: Gravity Forms + Custom Post Types] Undefined Index: setParentPost on line 65"

Hi! I try to use the plugin to generate posts almost like craigslist. The person posting has to pay with paypal (The addon in Gravity Forms) upon completion but when I'm trying to pass the form to PayPal I get an error stating "Undefined Index: setParentPost on line 65". What is this about and how to solve it?

http://wordpress.org/extend/plugins/gravity-forms-custom-post-types/