With the latest build on Jenkins I get this error when trying to enchant an item on a 1.8 server:
http://pastebin.com/s2wxpiz8

It might have been better to paste your log somewhere like Gist or Hastebin.

Updated

This is due to a change in EssentialsX for 1.11 which replaces deprecated methods which were only replaced in 1.9.

Simply downgrading to build 439 should work. You will no longer be able to receive EssentialsX updates though.