https://apps.facebook.com/cloudraiders/ When visiting this game, playing it for a bit, and then attempting to shut down the browser, the browser hangs. Eventually a stop script appears, and the user can then properly shut down the browser by asking it to stop.

Does the page have a beforeunload handler that ends up ilooping or something? If you do this in a debug build and then just drop into the debugger during the hang before the slow script dialog appears, what do the C++ and JS stacks look like?