Only one gallery not working

I have a really wird problem with nextgen – all of a sudden one specific gallery is not working.

There is nothing special bout it – it’s the sam as all the others, filesizes are below 150kB, filenames are short – around 30 characters, resloution is 800*600, 4 images in gallery. Both the images and thumbnails do not appear, on site nor in the backend.

however, if I click “edit thumb”, the thumb appears. Tried that with one thumb, nothing. Then I deleted the files and reuploaded them – the same. Once again I clicked on “edit thumb” and I noticed the previous thumb was mirrored – strange! That didn’t work either.

What could be wrong? There’s nothing, absolutely nothing unique about this gallery.