World generation bug that spawns a lot of zombies

Please fix this Mojang, there was a very annoying world generation bug that almost broke my Vanilla server. It spawned way too many zombies and made it so nothing would generate. I turned the difficulty to peaceful, and everything generated again but I cannot turn it back to Normal, Easy, or Hard because it will happen again. I was trying to build a wall around it because it looked ugly but when I placed a few blocks, water started spouting out. Please fix this so I can turn my server back to a better Difficulty. I can't figure out how to put the screenshots on here with my Windows 8.

-ogelspider2