Can you also explain why I point to the image precise_1_2010.jpg for gallery preview, but a different image is created at /wp-content/gallery/precise-faculty/dynamic/precise_1_2010-nggid03110-ngg0dyn-91×68-00f0w010c011r110f110r010t010.jpg?
Thanks, tizz and Cais. The combination of your answers resolved the problem. Tizz pointed me to the place where to look for the correct permissions. Somehow the permissions are not inherrited now, so I put all directories to 755 and all images to 644 manualy, but dynamic folders were not there at that point. Now I checked – the thumbnail images were their, but they had wrong permission. I fixed this.
My last question – is “non-inheritance” of permissions the problem of updated plug-in? We checked the folders in Linux, they should inherit correctly, yet they didn’t.