How To Fix Broken or Crashing iPhone Apps
Anyone who’s had an iPhone or iPod touch for a while knows that sometimes apps just stop working. In some cases a single app will stop working while the rest seem just fine. The first step is reboot your phone, but sometimes that doesn’t work. In that case, the solution is generally to delete the app from your iPhone and the re-download it.
However, in some rare instances, all of your third-party iPhone apps can stop working, even after a reboot. I’m not 100% sure why this happens, but it seems to be an issue with the FairPlay DRM database becoming corrupted. I’ve found that the best solution is to download another app from the App Store.
But wait, if all the apps are broken, why would adding another to the mix be of any help? To understand this issue, you need to know how your iPhone (and iTunes) handles apps. You see, each and every iPhone app has copy protection on it called FairPlay. To run an app, it needs to be unencrypted using a unique key which is generated by the App Store (aka the iTunes server). The key is given to your iPhone by iTunes to be stored in a local database so that apps can be run with or without data service. Although it sounds complex, it works quite well. That is, of course, unless that database becomes corrupted.
Because the iTunes server issued the keys in the first place, it can issue them again. The simplest way to accomplish this is to download an app from the App Store. It can be any app you want—free, pay, new, old—iTunes will refresh your key database just the same. After it’s been downloaded, verify that other apps run; they should. Once you’re sure everything’s back to normal, you can remove the new app without breaking things again.
Hopefully this helps out with your broken apps and, more importantly, helped you understand why it happens in the first place. If you still have issues, it might be time to restore your iPhone.