Hi,
Is the same happening with URL Loader available in the Develop tab?
Is the same happening with simple "Hello world" page?
Please note that the default color for background is black so in case you are displaying black text over black (default) background it won't be visible. Try setting white color to text or display some image.
Greets,
Tomasz
Same is behaviour with URL Loader app. When i launch any app under Develop tab i am getting black screen.