What version of jQuery script is required?

I have Visual Form Builder version 2.7.1 installed. What is the minimum jQuery version required? This plug-in has a conflict with my theme and the developer asked me that?

Does anyone have any ideas why the validation on this form isn’t working correctly: http://www.ofosa.org/wordpress/?page_id=854?

Thank you!!

http://wordpress.org/extend/plugins/visual-form-builder/