[andymoe]

First thing is double check you did not screw up the release. Like setting your deployment targeting to a lower SDK than your code supports normaly. It could be as simple as changing a drop down in Xcode.

Next check you did not start using a new method or function in the update that does not exist in the base SDK version you may be targeting. For instance there is no arc4random_uniform below 4.3 and will cause a crash. Look at some diffs from your earlier versions (you are using source control right) and see if you added any functions you are not really familiar with. Look for __OSX_AVAILABLE_STARTING in the headers where those suspect functions are defined or just double check the SDK docs.

Finally if your app needs specific phone features like front/rear facing cameras make sure non supported devices have been excluded correctly. That's the low hanging fruit that I would start with. Beyond that try and get your hands on one of your users crash dumps or a friends older device. Friends with jail broken devices tend to not update the os very often. Also, other iOS developers will horde older devices for testing so ask around at your local iOS meetup. Good luck.