So I've been working on this map for a few weeks now and suddenly this happened
(see attachment)

Basically the map has just gone dark and I cannot for the life of me figure out why. I was trying to create a mini map when this occurred and this problem seems to happen whenever I open up any of the backups of this particular map. Any help would be hugely appreciated!

What's that sphere that I see? Is that a light? Maybe you created a huge negative light?

That's an area sphere for rain. Thanks for the idea but there doesn't appear to be any negative lights :/