As Colorbox appends inline divs to the body tag, this is outside the form.
See http://markive.co.uk/blog/?p=13
Change this: $('body').prepend($overlay, $cbox.append($wrap, $loadingBay))
To this: $('form').prepend($overlay, $cbox.append($wrap, $loadingBay))
or search in the minified file for “body”, and replace it with “form”.
I also recommend prepending the project name to the min file and putting a comment the top stating it’s been customised.