I run a CraftBukkit (build #2974) server with EchoPet installed, I had version 2.2.4 on it then it told me to update to 2.3.3, so I did and when I restarted the server and joined it disconnected me every time, so I went back to version 2.2.1 and now I can't use pets in any worlds but the default one (it's not a permission problem I have *)

Human pets are re-enabled in 1.7.9 (EchoPet v2.2.4-SNAPSHOT)

What do you mean by it disconnected you (stacktraces and reasons are helpful)? If it had something to do with human pets, Mojang's UUID changes broke them in 1.7.8.

It said Disconnected from Server, there was no reason and the human pets still work on the server (it's 1.7.2)