Allright, here's the deal. I've just spent THREE hours trying to recover the world and server back to a usable state, with no luck. I've issued a rollback to May 26, 15:36 CST as I have no further options.
Near as I have been able to determine, this is NOT an issue with a corrupt chunk, or a chunk with too many entities. It is the setup that someone physically has in the world that seems to be causing it.
The problem seems to be that someone is running machines or other stuff that is bogging down the server immensely. If you have attempted to build something complex twice now before the rollbacks, DO NOT BUILD IT AGAIN without confirming with an admin first.