Hey! I just got a 5s a few days ago. Everything works perfectly, except that two times so far it's locked up completely (once in the camera app, once in Safari while on a page with a lot of flash content). It doesn't respond at all, to the lock button or the home button. The only way to fix it both times has been a hard reset (hold home button + lock button for a few seconds). Is this a known iOS7 thing? Or should I look at exchanging my phone? Do they have a backup stock for exchanges like this?