Microsoft released an HTML5 version of Cut The Rope which is pretty cool. Unfortunately they use Flash audio by default for Firefox users because, they say, "some Firefox users could have run into an audio problem but will notice we fall back to a flash plugin to ensure that sound effects and music will work." They don't mention specific Firefox bugs (although they do for Chrome), and when I try the HTML5 audio version it works fine for me. So, please try the HTML5 version in Firefox (release or nightly), and if it doesn't work let me know and file bugs! Thanks!