Odd. In Midori and Chromium, seems to work correctly. In Firefox, it appears crippled and I get 38 errors on the console -- SyntaxError, TypeError, ReferenceError -- including:

[09:42:19.907] SyntaxError: in strict mode code, functions may be declared only at top level or immediately within another function @ http://html5.grooveshark.com/build/app.min.js:1