Thumbnails not found in 2.0.66.17?

After upgrading, I’m seeing urls like this not finding an image in an album’s thumbnail of a newly created gallery:

http://localhost/wordpress/nextgen-image/14/91×68/crop/62a60a541482f122e0eef8acdd27f3ef

while a previosly created gallery shows a good thumbnail in the album:

http://localhost/wordpress/wp-content/gallery/test/dynamic/screenshot-from-2013-12-19-205138-nggid012-ngg0dyn-91×68-00f0w010c011r110f110r010t010.png

I tried regenerating thumbnails, restore-backup, it doesn’t seem to want to create an image. (this is in WP 4.0 beta 3).

Has the thumbnail system changed recently in this update?

https://wordpress.org/plugins/nextgen-gallery/