Definitely occuring for me again under 7.0.4... Try closing the app and re-running...
If i turn off basic auth from apache (that is i'm not changing my javascript), the app loads and runs, and when I re-enable basic auth from apache the app fails to load. So it has something to do with basic auth and not my code.
I must add that that when it fails it displays a prior startup image (which must be cached), rather than a whitescreen (no startup images) which the current app has.
I suspect there's some interaction with html5 AppCache and basic auth ... I'm not explicitly using AppCache (, that is loading a manifest...) but by default one's page is cached anyway.