App crashing when loading NIBs – but only after firmware upgrade to iOS 5-Collection of common programming errors

Some users of my app have reported crashes occurring only when opening the app after a firmware upgrade to iOS 5. Everything was fine prior to the firmware upgrade – including running the app and upgrading to a newer version of the app and then running it.

The crash log indicates the crash is occurring when a NIB is loaded:

0   CoreFoundation                  0x32bb38bf __exceptionPreprocess + 163
1   libobjc.A.dylib                 0x36a1d1e5 objc_exception_throw + 33
2   CoreFoundation                  0x32bb37b9 +[NSException raise:format:] + 1
3   CoreFoundation                  0x32bb37db +[NSException raise:format:] + 35
4   UIKit                           0x3169a747 -[UINib instantiateWithOwner:options:] + 1567
5   UIKit                           0x3160a9cb -[UIViewController _loadViewFromNibNamed:bundle:] + 247
6   UIKit                           0x314e9ea1 -[UIViewController loadView] + 89
7   UIKit                           0x3145f78b -[UIViewController view] + 51
8   UIKit                           0x3146bc39 -[UIViewController contentScrollView] + 25
9   UIKit                           0x3146baa9 -[UINavigationController _computeAndApplyScrollContentInsetDeltaForViewController:] + 37
10  UIKit                           0x3146b98f -[UINavigationController _layoutViewController:] + 35
11  UIKit                           0x3146b211 -[UINavigationController _startTransition:fromViewController:toViewController:] + 501
12  UIKit                           0x3146af53 -[UINavigationController _startDeferredTransitionIfNeeded] + 251
13  UIKit                           0x3145f673 -[UINavigationController pushViewController:transition:forceImmediate:] + 807
14  UIKit                           0x3145f349 -[UINavigationController pushViewController:animated:] + 37

For some reason, deleting and reinstalling the app after the iOS 5 firmware upgrade seems to resolve the issue.

I’m utterly baffled as to what the cause could be. I’d really appreciate any thoughts you may have.

Thanks in advance!