1) regular user signs up for an event
2) user checks their sign-up information
3) User clicks the EDIT button, but fields are stilled greyed out and they cannot change anything. Everything works fine for Internet Explorer.

Comments

I temporarily solved this by commenting out the js/signup_edit_form.js file. Basically the jquery function just looks like:

(function ($) {
Drupal.behaviors.enableSignupEditForm = {
}
})(jQuery);

I am actually okay with NOT having this fancy-schmancy jquery effect and letting users quickly be able to edit the fields right away.

Perhaps someone else can take the time to fix the jquery problem that is not working in Firefox 13