Kasper,
The problem is that Mootools isn't loading on the page. Looking at your HTML code, you're using the Google API library to try to load Mootools, instead of hosting it. The line for google.load of mootools is present. The line above it, loading the Google JSAPI is commented out though. Without that, the google.load call is failing.
I think that's the issue. I've never used the Google JSAPI loader before though, so this is new to me. I think when you fix that though, your validation issue will be as well.
Thanks,
Alex