add_meta_box suggestedtags

“Warning: call_user_func() expects parameter 1 to be a valid callback, first array member is not a valid class name or object in …/wp-admin/includes/template.php on line 297”

I don’t know how to solve this problem, if could someone can help me please release me of headaches.

The code:
[backticks]add_action(‘admin_init’, ‘stags’);

function stags() {
add_meta_box(‘suggestedtags’, __(‘Suggested tags’, ‘simpletags’), array(&$this, ‘boxSuggestTags’), ‘videos’, ‘advanced’, ‘core’);
}[/backticks]

http://wordpress.org/extend/plugins/simple-tags/