Oh wait, I think I may know what this is. Can you try this - remove the textures, commmit, then add the new textures, and commit again?
p.s. If this is causing the issue, I'll be releasing the new editor (completely rewritten) very shortly now. Just doing some final tests now to make sure its backwards compatible to older versions of 2D Toolkit. This completely gets rid of all these issues, and also adds multi select & edit, etc.