Help with lightbox gallery mode

[Gribnif]

I'm having trouble getting lightbox galleries to work. When the lightbox opens, the image and navigation arrows are displayed, however clicking on an arrow does nothing. I've traced through the code and found this line:

    function advanceGallery(e) {
      Functions.killEvent(e);

      var $control = $(e.currentTarget);

      if (!Instance.isAnimating && !$control.hasClass(RawClasses.control_disabled)) {

Instance.isAnimating stays true. This seems to be because this transition never completes:

          Instance.$content.fsTransition({
              property: "opacity"
            },
            function() {
              Instance.$lightbox.removeClass(RawClasses.animating);
              Instance.isAnimating = false;
            });

The second function() is never called. Have you seen this before?

[Gribnif]

Some more details: If I manually modify the div.fs-lightbox-content container, and set the background attribute to 0, the code gets triggered. Apparently, there is something amiss in the way completion of the opacity transition is being detected.