Multiple users have been reporting crashes with 1.8.3. The logs indicate the error in the refreshChunks area. I have not changed my plugin code, only the server has been updated. I have not been able to replicate myself on git-Spigot-c136710-350cb99, but I can't load my own server. A user says that it is present on the latest version:

Version: [12:53:35 INFO]: This server is running CraftBukkit version git-Spigot-c136710-0af2738 (MC: 1.8.3) (Implementing API version 1.8.3-R0.1-SNAPSHOT)
[12:53:35 INFO]: Checking version, please wait...
[12:53:36 INFO]: You are running the latest version This was present before and after.

http://pastebin.com/zMWXDQEn
also previously:
http://pastebin.com/zhRzJ7MH