UIStepper throwing an exception

I'm getting this when I click on the UIStepper button

Objective-C exception thrown.  Name: NSInvalidArgumentException Reason: -[PlannedCrops stepCrop1:]: unrecognized selector sent to instance 0x7c3065f0-  at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
  at MonoTouch.UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0004c] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:38 
  at ftrack2ios.Application.Main (System.String[] args) [0x0000a] in /Volumes/Developer/Developer/ftrack-2/iOS/ftrack2-ios/ftrack2-ios/Main.cs:18 

Any ideas why this is happening.

I have the steppers set as outlets and sit on the ValueChanged event. As soon as the button is clicked, kablooey, app dies.