I have seen this, or something similar, happen several times. My experience is that it happens when you do two consecutive uploads of the same species. The second sighting does not work and returns a blank screen. I have not found a way of clearing the condition, whatever it is. I would suggest trying a different browser for the upload/edit. I don't know why I did not try this myself when I had the problem. Another possibility would be to clear the cookies for naturemapr but I'm not sure if the problem is on the client or on the server side.