Black screen just on the top

I have what’s probably a stupid problem but I can find out why I’m having it. When I build my app and lunch it on the device almost every time the screen get’s black only on the upper part of the screen, but I can still see all my image. It’s like my screen get smaller!
Any ideia why and how to fix it? [import]uid: 32005 topic_id: 8468 reply_id: 308468[/import]