[maya] - instanced meshes, GONE! help!

bugo

So, for some reason, whenever I exported a last FBX file, and then saved my file after it, all the instances in this file are gone, and this also happens after opening it another time. While going through dropbox, I've tried to get older versions, but the same problem occurs. Is there something with FBX or something in Maya that I dont know a clue about that is making my instance meshes to dissapear?

bugo

WTF! after deleting all the meshes, and undoing, THEY've APPEAR! Still, I don't want it to happen again, anybody, any clues of what's going on?