Reason why UIImageView gives me a 'distorted' image sometimes

Question

I have a custom UIView with a UILabel and a UIImageView subview. (tried using UIImageView subclass aswell). I assign an image to it and add the view to the screen. I wrote a function which adds the amount of LetterBoxes to the screen as there are letters in the word:

- (void)drawBoxesForWord:(NSString *)word {
if(boxesContainer == nil)
{
    /*
     Create a container for the LetterBoxes (animation purposes)
     */
    boxesContainer = [[UIView alloc] initWithFrame:CGRectMake(0, 205, 320, 50)];
    [self.view addSubview:boxesContainer];
}

/*
 Calculate width of letterboxes
 */
NSInteger numberOfCharacters = [word length];
CGFloat totalWidth = numberOfCharacters * 28 + (numberOfCharacters - 1) * 3;
CGFloat leftCap = (320 - totalWidth) / 2;

[letters removeAllObjects];

/*
 Draw the boxes to the screen
 */
for (int i = 0; i < numberOfCharacters; i++) {
    LetterBox *letter = [[LetterBox alloc] initWithFrame:CGRectMake(leftCap + i * 31 , 0, 28, 40)];
    [letters addObject:letter];
    [boxesContainer addSubview:letter];
    [letter release];
}}

This gives me the image below:

http://www.imgdumper.nl/uploads2/4ba3b2c72bb99/4ba3b2c72abfd-Goed.png

But sometimes it gives me this:

imgdumper.nl/uploads2/4ba3b2d888226/4ba3b2d88728a-Fout.png

I add them to the same boxesContainer but they first remove themselves from the superview, so it's not like you see them double or something.

What I find weird is that they are all good or all bad.. This is the init function for my LetterBox:

if (self == [super initWithFrame:aRect]) {
    /*
     Create the box image with same frame
     */
    boxImage = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height)];
    boxImage.contentMode = UIViewContentModeScaleAspectFit;
    boxImage.image = [UIImage imageNamed:@"SpaceOpen.png"];
    [self addSubview:boxImage];

    /*
     Create the label with same frame
     */
    letterLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height)];
    letterLabel.backgroundColor = [UIColor clearColor];
    letterLabel.font = [UIFont fontWithName:@"ArialRoundedMTBold" size:26];
    letterLabel.textColor = [UIColor blackColor];
    letterLabel.textAlignment = UITextAlignmentCenter;
    [self addSubview:letterLabel];
}

return self;}

Does anyone have an idea why this could be? I'd rather have them display correctly every time :)