My app has been running fine with Unity 5.1 then I updated to 5.3 so I can take advantage of the new Services feature. I also updated PUN to 1.65 and when I ran the latest build the app crashed in PhotonNetwork.cs. I am not all that great at debugging in Xcode as I have been building my app in Windows, but it appeared the app crashed when attempting to do the line "Application.runInBackground = true;" in PhotonNetwork.cs. I reasoned that this line of code didn't do anything for mobile apps as iPhones and such can't actually run in the background so I simply commented out this one line of code and it fixed the crash issue.
I'm posting this in case others may have the same issue and as a bug report.
I'm posting this in case others may have the same issue and as a bug report.