I have a Zenphoto install I've used for many years. It's currently at version 1.4.1.3 I just tried to add an image to one of the Albums, using the built-in Upload. It appeared to work fine, but when I click on the image Thumbnail, instead of getting the full size image, I see a LINK made up of the image's title. When I click on that link, the full size image appears.

Is this a configuraiton thing that I have long since forgotten about?

SOLVED: It was a cache issue, both for the thumbnail display, AND for the large image display. Required two separate browser cache clears, one for the thumbnail page, and one for the image page.

Good you solved it. But you should really consider to upgrade… 1.4.1.3 is nearly six years old and that would be the first we would have told you if you hadn't solved it yourself.