I am having the weirdest problem. I was doing some heightmap manipulation outside the city I am building right now, and when I went in-game to test my mod, one cell had just sunk to the bottom. The stuff I had placed on it, trees and brushes and things are still in their correct location, but the entire ground of the cell has just sunk under water. The problem is that i can't get it back up to its intended level, but the entire cell stays there and it doesn't help to try and heighten the ground. All my npc's also fall off the edge into that cell when they get close and they come back up swimming over land looking stupid.

The infected cell is 0,0 in my worldspace.

Has anyone had anything similar and how do I solve it?

Disregard. I solved it. I finally was able to edit cell 0,0, and could raise the ground again. Lucky for me, I didn't have much in cell 0,0, but just a small docks and a harbour, but it also affected the entrance to my city. Oh well, the ground is back in place and it even looks better than before the accident. I won't ever use the heightmap editor without care again.

Phew!