We’re not using the app. It’s already been stated in this thread that we're playing through Facebook on the Firefox browser. Downloading the app isn’t even an option in Windows 7.
I've been having the same problem. It's been almost a week. When I try to play it on my desktop through facebook it loads normally but then the screen goes black. You can still hear the music in the background but you can't see anything. I'm running Windows 7 on Firefox. Here's a pic of what I'm seeing: