Custom images with UISlider doesn't show on the device.

Programmer Question

Everything works on the simulator without a problem. However when I put it on my device it only show the ThumbImage. It is just really strange. I'm thinking this could be a iOS version issue or memory issue. My device is iPhone 3GS iOS 4.1.

@interface BlueChalkSlider : UISlider {}
@end

@implementation BlueChalkSlider
- (id)initWithCoder:(NSCoder *)decoder {
    if ((self = [super initWithCoder: decoder])) {      
        self.backgroundColor = [UIColor clearColor];
        [self setThumbImage:[UIImage imageNamed:@"Chalk.png"] forState:UIControlStateNormal];
        [self setMinimumTrackImage:[UIImage imageNamed:@"ChalklineBlue.png"] forState:UIControlStateNormal];
        [self setMaximumTrackImage:[UIImage imageNamed:@"ChalklineWhite.png"] forState:UIControlStateNormal];
    }
    return self;
}
@end

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