It seems there’s a limit on the number of attachments of a post?
I have 265 images uploaded for one of the posts (yes, I know it’s quite a few), and when I want to put them into order. The result: only 125 of them gets number, the others a left without one and also I only see 140 images.
The tabs says “gallery (265)”, and it is ok, but I only see 140 images when I open the gallery tab.
Just tested with WordPress 3.4.2 and 3.5.2-beta2.
With 317 files, this issue does not comes up (order or maximum number of shown items).