iOS 4.3.2 user reported app crashing on launch

An update of my app has just been approved by Apple and users are now complaining the app does not launch anymore. It also happens to some new users.

I have absolutely no idea where the problem is nor can I reproduce the problem. I have tested the update on various devices (& simulator) before submitting the update: iPhone 2G running 3.1.3, iPod Touch 2G running 4.3 , iPhone 3G and iPhone 4 running 4.3.1. They ALL work as expected. The update has a few new features like random picking photos from user's photo library using AssetsLibrary framework, I have weak-linked the framework to support iOS 3 and the feature does not load until selected by the user so it should not be the problem. After all, the update has been tested and approved by Apple.

I have difficulty collecting crash information from users with the problem, but I know one of them uses iPhone 4 with iOS 4.3.2. A quick google search reveals that iOS 4.3.2 has problems launching third party apps, I suspect my problem has something to do with this but I can not confirm it. I am planning to downgrade my dev iPhone 4 to iOS 4.3.2 to test it.

Does anybody here experienced similar problem? My app's ranking has dropped significantly because of the negative reviews so I need to fix this as soon as possible.

Edit:

• There should not be any watch dog problem, I tested the update on the above mentioned devices with and without Xcode/debugger.

• Memory management. I can not reproduce the problem (I tried quite hard) so I can not confirm if it's EXC_BAD_ACCESS, I did check reference count and nil released objects (safely release) when applicable, I am absolu开发者_如何学编程tely not a pro in memory management so I take it seriously, I checked leaks and allocations with instruments, stress-tested and did memory warning simulations, no problem was found.

• I have UIApplicationWillEnterForegroundNotification in -loadview, it's only available after iOS 4.0 so I check if it exists with & operator because I use it.

• I do not persist data other than saving facebook connect token and expiry date (NSDate) in NSUserDefaults, since the problem also happens to new users so I think it's something else

We're going to need more info, unfortunately. But just off the top of my head:

• Watch dog? What sorts of stuff are you loading when you launch your app? It may be that resources are constrained on the devices having this issue and you are doing work that should be done a separate thread, or otherwise delayed until after the app has launched.

• EXC_BAD_ACCESS. There could be a race condition going on that is resulting in most people able to launch OK, but for some it just isn't working because of bad references. I know, you write good code and manage your references like a pro, but sometimes a non-obvious slip-up can creep in.

• Are you safely instantiating some types of classes? An example that bit me once was with the MFMailComposeViewController class. Before instantiating you're suppose to call its static method canSendMail. If a user hasn't setup any mail accounts on their device (hard to figure there would be anyone that fits this scenario, but hey! found out after an update that there are quite a few!) then the app would crash.

• What data persistence (if any) do you have? Are you using Core Data? Serialized objects in a plist? NSUserDefaults? Your strategy may be corrupting data you are persisting and that is leading to a crash.