Crash when Starting Ftb Ultimate Server

Hi, I made an FTB Ultimate Server yesterday and it was working completely fine, now when i try to start it, this comes up.....

---- Minecraft Crash Report ----
// My bad.

Time: 16/03/14 2:59 PM
Description: Exception in server tick loop

java.lang.NullPointerException
at org.bukkit.craftbukkit.CraftChunk.getWorld(CraftChunk.java:70)
at org.bukkit.event.world.ChunkEvent.<init>(ChunkEvent.java:12)
at org.bukkit.event.world.ChunkPopulateEvent.<init>(ChunkPopulateEvent.java:16)
at...

Crash when Starting Ftb Ultimate Server