The images always popup in a double lightbox, 1 covering the other, and thus 2 different lightboxes have to be closed after viewing the images. The front box has a white border, hiding the other one, which has a black border
I've tried uninstalling and reinstalling several times but the result is always identical.
I actually love the plugin itself for its simplicity of use and its clean and clear presentation of the pictures. But the double lightbox is a definite fun spoiler.
You can judge for yourself here: zee.vandijck.org/index.php/beeld

BTW you'll also notice the troublesome JW_SIG_NAVTIP caption I have not been able to remove, in spite of all hints given on this forum (including fixing permissions, renaming ini files etc.)

This is a conflict with MediaBox plugin you use.
The caption issue will be solved with the new version we will release soon.
At the moment you may hide them by adding this in SIG css folder.
#lbCaption {
  display:none;
}

The caption item is now solved. And I'll be looking out for your new release.

As to the double lightbox: for the time being I have simply disabled the system Mediabox plugin and the issue has disappeared. I still need some checking to see whether there is any functionality lost somewhere else, but so far it all seems pretty normal.

So, many thanks for your reply. You have made me a happy SIG'er again.

You are welcome! ;)