[eluser]WanWizard[/eluser]
First of all, don't use plugins. They are deprecated and will no longer be supported in CI 2.0. Use a helper instead (they're the same thing anyway)
How do you load your library? It looks like $this->load doesn't work in your library, so the plugin is not loaded, and therefore the call to the plugin fails.
$this->load doesn't work in constructors, so use
Code:
$CI =& get_instance();
$CI->load->plugin('plugin');