Help with plugin that says the theme is the probem.

Hey there.
I am trying to use the Cutsom Contact Form plug-in by Taylor Lovett on my site. It works great on all of the browsers except Firefox. I've contacted him and his response was, "Hey, this is just a CSS issue in your theme. It should be easily resolvable." I asked him to clarify, but haven't heard from him. Can you help? This form is perfect for what I need but the issue with firefox is that the check boxes and radio buttons don't show. They work in all of the other browsers I tried. Opera, Chrome, Safari. Firefox! It's not the first time for me that FF doesn't play nice with Upfront.
You have access to the site. Any help would be appreciated.
Terry