Why is this happening to my server? Please help.

Ever since the 1.4 craftbukkits' came out, I am able to use them but I cannot play on the server with it. I cannot use commands and plugins, My world is cut which means it has chunk error and does not load. I cannot see other players, cannot save the world and after a while it says:
"* Player-name* is now AFK". I need help because my friend's server works on it but not mine.
If wanted, I can provide screenshots.
Many Thanks.