In your httpd.conf file you should have two lines that load the plugin module and the xml file.

Example for Windows:
LoadModule was_ap20_module c:\Program Files\IBM\HTTPServer\Plugins\bin\mod_was_ap20_http .dll
WebSpherePluginConfig C:\Program Files\IBM\HTTPServer\Plugins\config\webserver1\plu gin-cfg.xml

You appear to have the essentials, as the plugin in loaded. I would check to make sure that the web server is loading the correct plugin-cfg.xml file. Check to make sure your XML file has been updated with your updates. If you do not know what to check, you may want to post the XML that is being pointed to in the httpd.conf file.