Issue applying DD_belatedPNG png fix on images within a lightbox (IE6)

Question

I am trying to invoke the DD_belatedPNG fix on images within a lightbox once it has been called. Okay, so that's easy enough with colorbox:

$(el).colorbox({
  ...
  onComplete:function(){
    DD_belatedPNG.fix('#product_pop .fixme');
  }
});

This works fine, and the pngfix is applied BUT it only works the first time the lightbox is called, all subsequent calls to the lightbox don't seem to have the PNG fix applied :S

I've also tried calling the pngfix only for that first time that the lightbox is opened, and each subsequent view, do nothing (as per the example below) - but that doesn't seem to help either.

Example here