[Antithasys]

It appears that you are mix and matching some versions. It is in the .inc file that is part of the .zip file that is in the OP.

The Simple Plugins have been undergoing major changes on the SVN/Project Site, and yes, we have removed that native from the core and just went with a stock function in the core-sm.inc file.

This version works just fine, but we have significantly modified this plugin in the beta. If you have the ability, feel free to install and test the beta that is located on the project site... feedback on its features and such would be great.