Wont it start? black screen?
Anyways there a few things you can try:
First refresh the page (maybe several times).
Update your flashplayer.
Maybe cleaning up your browsers cache (not the "normal" tempfiles/cookies, the browser-cache is something differen, maybe google it... but this is a shot in the dark, its msotly working if a game wont load the latest version)
And, as winmaster mentioned, try another browser.
