The only issue I had was that when you played for long enough the game slows down. The only way to fix it is to reload the page. I've had a similar problem before, and it was caused by using code attached to keyframes in movie clips in order to have multiple animations in a single movie clip. As long as the clip continues to play, the garbage collector does not remove it, even if you delete it in your code. To fix this, simply run stop() on the movie clip. Just a guess.