Iphone : Applying strechable images to a button disables it

I am sure I am doing something stupid here. I build a category on top of UIButton which I want it to take all of the background images assigned to it (different states) and convert them to stretchable versions and reapply them back to the button.

- (void)enableBackgroundImageStrechingWithLeftCapWidth:(float)leftCapWidth withTopCapHeight:(float)topCapHeight;
 {
 
     UIImage *backgroundimageNormal = [self backgroundImageForState:UIControlStateNormal];
 
     if (backgroundimageNormal != nil) 
     {
         UIImage *stretchImage = [backgroundimageNormal stretchableImageWithLeftCapWidth:leftCapWidth topCapHeight:topCapHeight];
         [self setBackgroundImage:stretchImage forState:UIControlStateNormal];
     }
 
     UIImage *backgroundimageSelected = [self backgroundImageForState:UIControlStateSelected];
 
     if (backgroundimageSelected != nil) 
     {
         UIImage *stretchImage = [backgroundimageSelected stretchableImageWithLeftCapWidth:leftCapWidth topCapHeight:topCapHeight];
         [self setBackgroundImage:stretchImage forState:UIControlStateSelected];
     }
 
     UIImage *backgroundimageHighlighted = [self backgroundImageForState:UIControlStateHighlighted];
 
     if (backgroundimageHighlighted != nil) 
     {
         UIImage *stretchImage = [backgroundimageHighlighted stretchableImageWithLeftCapWidth:leftCapWidth topCapHeight:topCapHeight];
         [self setBackgroundImage:stretchImage forState:UIControlStateHighlighted];
     }
 
     UIImage *backgroundimageDisabled = [self backgroundImageForState:UIControlStateDisabled];
 
     if (backgroundimageDisabled != nil) 
     {
         UIImage *stretchImage = [backgroundimageDisabled stretchableImageWithLeftCapWidth:leftCapWidth topCapHeight:topCapHeight];
         [self setBackgroundImage:stretchImage forState:UIControlStateDisabled];
     }
 }
 

Seems to work except the button is now not clickable

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