I get a similar message when I access our demo site, but I still see the button:
Screen shot 2010-04-11 at 9.37.50 AM.png
This is where that image is coming from (for me at least):
[url:5ltkse45]http://static.ak.fbcdn.net/rsrc.php/zEYEC/hash/7e3mp7ee.png[/url:5ltkse45]
Can you open that image in your browser directly?
Let me know what you find and we will keep trying stuff.