AdditionalDebugHooks are only included when the app is compiled in debug mode, they're excluded when the app is compiled in release mode.
CustomPrepareStart and CustomPrepareEnd are in the
Prepare::FieldEquate
routine - for Progress Bar controls.
So if you changed a field equate, or changed the field from being a progress bar, or deleted a progress bar field, then you'd get this.
cheers
Bruce