A method is called when a return button on the keyboard is pressed. After calling another method which returns an integer a message is created based on that integer. The message
Try it with NSZombieEnabled = YES.
When the memory is released that has already been released, NSZombie will display the address, then you can use Instruments to find the actual object. Corbin's Treehouse has a good overview of how to do this: Instruments on Leopard: How to debug those random crashes in your Cocoa app