Go to http://www.unrealengine.com/html5/ click try anyway (because why wouldn't you UA check for an open&safe API?), when it fails click on one of the errors.
The inspector tries to go to the source map file, even though it has already seen that file can't be loaded. This makes it difficult to debug :-/
Moving to the right component.
This does not repro for me any more. Please reopen if you identify another test case.