I just took a glance at your source code. You're loading jQuery twice on the same page - the firs time it's the native one that's included into the WordPress core (version 1.7) and the second one next to NivoSlider code (version 1.5). That's asking for trouble right there.
Make sure you remove the jQuery version 1.5. It might be bundled with NivoSlider. If so, deactivate the slider - make sure the codes doesn't load on the page.
If you don't see calculator throwing errors, don't assume it's broken - start taking care of the errors that are obvious.
Hope this helps.