random BAD ACCESS when saving user defaults

Question

I'm simply trying to save this array to the user defaults and it will crash at random. Sometimes it works, sometimes it gives me the EXC_BAD_ACCESS. Am I not releasing something properly?

- (void)setTextValue:(NSString *)valueText indexToSet:(NSUInteger)index
{
    [self.pageData replaceObjectAtIndex:index withObject:valueText];
    [[NSUserDefaults standardUserDefaults] setObject:self.pageData forKey:@"mynotes"];
}

Here is the method that i've determined is causing the errors. It was a method already created by Xcode that I added my own custom code to.

- (nbookDataViewController *)viewControllerAtIndex:(NSUInteger)index storyboard:(UIStoryboard *)storyboard
{   
    nbookDataViewController *dataViewController = [storyboard instantiateViewControllerWithIdentifier:@"nbookDataViewController"];
    if (self.pageData.count > 0 && index < self.pageData.count)
    {
        NSString *val = (NSString *)[self.pageData objectAtIndex:index];
        dataViewController.dataObject = val;
    }
    else
    {
        NSDate *date = [NSDate date];
        NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
        [dateFormat setDateFormat:@"MMMM d, YYYY"];
        NSString *dateString = [dateFormat stringFromDate:date];
        //[dateFormat release];
        [self.pageData addObject:dateString];
        dataViewController.dataObject = (NSString *)[self.pageData objectAtIndex:index];
    }
    dataViewController.myModel = (nbookModelController *)self;
    dataViewController.dIndex = index;
    //[self.mySaveData setObject:self.pageData forKey:@"mynotes"];
    return dataViewController;
}

Answer 1

This tip will allow you code to break on the exception and let you check directly why this is happening: https://stackoverflow.com/a/616526/46970