iOS crash when built with one version of Xcode, no crash with another version

I need to debug a crash that happens at a fundamental part of the app experience on a particular iOS version, but when I use the (newer)开发者_StackOverflow社区 dev tools for that version, the crash does not occur.

How can I get a GDB session on version of an app that was installed with another SDK version?

See if you can build the app in Xcode 4.1 and deploy it to an iOS 5.0 device via TestFlight: https://testflightapp.com/