They are little BLUE arrows.

The photos are being displayed. The page dims to a dark shadow and the picture still loads in the middle of the screen. However, there should be (I recall) green arrows on the bottom to help navigate from picture-to-picture.

Not entirely sure when this feature was lost, and I'm attributing it to some of the plugin upgrades that have occurred over the last 4 months or so.

During the summer holidays coming up, I'll be looking to restore most functions again, or at least have a workaround for some of these little bugs here and there.