addSubview does not show view on iOS 3.1.3

I have a scroll view which has one UIView inside which contains the content. I am adding a UIImageView as a sub of the UIScrollView (so it should be on top of the content container) and this works on iPhone 3.2+, but on an iPhone running 3.1.3 the image does not show up above the container. My code is something like this:

    // add the content container
    UIView *contentContainer = [[UIView alloc] init];
    [scrollView addSubview:contentContainer];

    // add content, etc

    // this works in 3.2+
    UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
    [scrollView addSubview:imageView];
    // tried adding this for 3.1, but still didn't work
    [scrollView bringSubviewToFront:imageView];
    [imageView setFrame:CGRectMake(point.x, point.y, image.size.width, image.size.height)];

Is there something else that I'm missing? Thanks!

Are you also actually setting the contentSize property of the UIScrollView ?

Found the issue: when I specified the image name, I was not specifying the image extension:

UIImage *image = [UIImage imageNamed:@"myImage"];

If I change this to the following, it works:

UIImage *image = [UIImage imageNamed:@"myImage.png"];

Does iOS know to still look for the "@2x" version if available when the extension is present by chance?