I don't recommend even trying to use the lightbox...

The lightbox concept is supposed to work thus... as you browse the galleries and click add to lightbox a list is built which will generate a zip of all the images you've added. At some point, this zip file of images is downloaded to your computer for your use. This is supposed to save you the hassle of downloading the individual images and will download faster in zipped format.

Personally, I've never gotten the lightbox to work for me in a logical way, although it has occasionally downloaded the zip file... but not when I expected it, and sometimes multiple times. We're running a very old version of the gallery software and so the problem may be fixed in a later release (which we'll eventually either upgrade to or replace with a different/better gallery program).

I spent some time browsing the innards of the gallery structures this morning and didn't find a zip file waiting for download, so honestly I don't know what's wrong. There's no configuration option to disable the feature. Let me know if the problem continues to persist after a couple days and I'll investigate more thoroughly. I seem to recall that the zip file didn't appear for a day or more when I investigated the lightbox about a year ago.