The box is working actually. The logged in user is seeing the full size image, guests see a shrunk down version. If you go to the gallery, click on My Profile, click Edit on My Information and set View Image Width to something like 400. You'll see what I mean. I'll look and see why the enlarge checkbox is showing. It might be that it's a pixel or two larger and it is working, it's just so small you don't see the difference.