/kill command takes a few seconds to execute when typed

When /kill is typed into the chat and executed it does nothing for about 3 seconds then executes as normal giving the death message and killing the player. Here is the console log:

Client> 2013-06-15 18:43:40 [SERVER] [INFO] blobjim fell out of the world
Client> 2013-06-15 18:43:40 [SERVER] [WARNING] Can't keep up! Did the system time change, or is the server overloaded?
Client> 2013-06-15 18:43:40 [CLIENT] [INFO] [CHAT] blobjim fell out of the world
Client> 2013-06-15 18:43:40 [CLIENT] [INFO] [CHAT] Ouch! That looked like it hurt