Carrot tree crashing 1.4.6 server

On a randomly spawned survival map friends and I changed to creative to create an adventure map however after searching around the place, the server started to crash randomly producing the exact same report each time.
Only now when I was looking at the badly generated map I found the problem and the server crashed. I told my friend to go over to it and the exact same thing happened

When this...thing... (shown in the attachments) loads, the server crashes completely