[Konstantinos]

Then do you load nativechecker plugin before Whirlpool? If yes, the message will be given and as the important note in the nativechecker plugin's thread says: it must be loaded last.

If your server doesn't start, it can be any reason. If you use MySQL, then check the logs. The connection might fail. Load crashdetect plugin just in case it's a server crash.

EDIT: Yes, you do.