Iphone – Core data / NSFetchedResultsController error

I'm having some trouble with core data / NSFetchedResultsController. I'm not entirely sure where the error is as the message is quite vague.

I have an issue with inserting more than one object when the fetched results controller has no objects fetched. The following code will crash with the following error if I try and insert several objects with none fetched already. It doesn't crash if I use it to insert one object, and it doesn't crash if there are already objects fetched.

The crash occurs on the save: method. titles in an NSArray and in this example it contains 5 strings.

Serious application error. Exception
was caught during Core Data change
processing: * -[NSCFArray
objectAtIndex:]: index (4) beyond
bounds (1) with userInfo (null)
* Terminating app due to uncaught exception 'NSRangeException', reason:
'*** -[NSCFArray objectAtIndex:]:
index (4) beyond bounds (1)'

NSEnumerator *titleEnumerator = [titles objectEnumerator];
NSString *title;
NSMutableArray *tasks = [NSMutableArray array];
Todo *todo;

while(title = [titleEnumerator nextObject])
{
    todo = (Todo *)[NSEntityDescription insertNewObjectForEntityForName:@"Todo" inManagedObjectContext:managedObjectContext];
    todo.title = title;
    todo.state = [NSNumber numberWithInteger:TodoStateIncomplete];
    todo.priority = [NSNumber numberWithInteger:TodoPriorityNormal];
    todo.timeStamp = [NSDate date];
    todo.dueDate = [NSDate distantFuture];
}

NSError *error;

if(![managedObjectContext save:&error])
{
    NSLog(@"Unresolved error %@ %@", error, [error userInfo]);
    abort();
}