In form-output.php south of line 160 you're conditionally adding style="display:none;" based on whether a user is logged-in or not. When they are, this means the resulting <li> tag will have two style attributes which might be fine in most browsers but will most certainly break most strict DOM parsers, including a JS library I'm using.
My fix involved setting $logged_in_display = ' style="display:block;" above the is_user_logged_in() check, and remove the style attribute from the sprintf statement below if block.
Great job, thanks for the excellent plugin.