@cais: I can confirm that Reset All Options To Default Settings and then Clear Image Cache worked for me too. Thanks!
Bruce
I’m also having this problem, after upgrading to WordPress 4.3.1 and NGGallery 2.1.15 today. I tried clearing the image cache as suggested by @photocrati, but am still having the problem.
It was working fine with WordPress 4.3.1 and the old version of NGGallery, but once I updated the plugin to 2.1.15, it stopped working.
