Thanks for sending me the files!
Hm, that atlas works just fine for me! Two things you could check:
1) the "name" in the "SubTexture" element includes the extension — e.g. "illuminada.png". To access the texture, you have to pass that extension, too. Have you done that?
2) Have you added both the @2x and the normal resolution?
I think both cases would end up with that exception (accessing the subtexture without the extension or running in a non-retina device/simulator without the standard resolution texture being available).
Could it be one of those?