Your page includes MooTools 1.4.5 compiled with compatibility mode enabled. MooTools compatibility mode overrides modern browser interfaces, breaking JavaScript such as Twitter’s widgets-js relying on those interfaces. Updating your JavaScript to a nocompat version of MooTools should fix the issue.
Build a new version of MooTools with the compat layer build option left unchecked.
http://mootools.net/core/builder
You could also use a hosted version on a CDN, swapping your current script src. Look for nocompat in the filename to indicate the hosted JavaScript was compiled without the compatibility flag enabled.
