The latest versions of NS Formula that are used on Joomla 3+ requires bootstrap for the buttons and fields to display properly.
Unfortunatly the Beez3 template that is included with Joomla 3.0 (and newer) does not load the necessary bootstrap CSS.
The easy work around is to install a bootstrap plugin. We have sucessfully tested http://extensions.joomla.org/extensions/style-a-design/templating/19761 on Joomla 3.0 and 3.1 and found it loads the necessary bootstrap files so the formula module displays properly.