I have a required field for customers to select a shirt size (I'm also using the PayPal plugin). I've tried using all the options for the choices (dropdown, radio buttons, checkboxes). The only way I don't get the error message for "required field" even when I've selected something, is by using the checkbox option. However, even when choosing a checkbox, the form and payment will process, but the t-shirt size choice is not carried forward onto the entry file (neither the email or our server side copy).
I'm using StudioPress Genesis Focus child theme, and I've deactivated a widget plugin I was using with a rotator function... to no avail. Live form is here:
http://www.habanapalooza.com/tickets/