Bukkit

What steps will reproduce the problem?
1.
2.
3.

What is the expected output? What do you see instead?

What version of the product are you using?
The newest version

Do you have an error log of what happened?
"An internal error occurred while attempting to perform this command"

Please provide any additional information below.
if i am doing /md, its says something about the Plugin, but when i am doing /md [mob] it doasn´t work