title: Where to start debugging app built with iOS 5 that runs on 6 but not 5.1?
body: <p>I have an app that needs to support 5.1 devices.</p>
  
  <p>It runs fine on an iOS 5 iPhone, but not an iPad.  On iPad with iOS 5.1.1 it just hangs.  I am not sure how to go about debugging it.  I have commented out everything in <code>didFinishLaunchingWithOptions:</code> but after the end, I just hangs.  If I pause the app it stops at <code>mach_msg_trap</code>, which is not much help... at least to me.</p>
  
  <p>If I run the same app on the iPad 6.0 simulator, it works fine.  I have built the app with the 5.1 SDK and have tried it in all simulators.  </p>
  
  <p>Any help on where to start would be appreciated.  I am not even what sure what details to give for help.</p>