WordPress MU

Hi,
Just trying out the simple MyEvents plugin (http://wordpress.org/extend/plugins/myevents/). There is a problem when trying to delete an entry in the list of events. The global value $wpdb isn't available in the function called. It's available elsewhere in the same class.
I presume this is because of the way the delete function is called:

if (isset($_POST['action']))
{
	if ( $_POST['action'] == 'options' ) {
		$myevents->settings['pattern'] = $_POST['pattern'];
		$myevents->save_options();
	}

	if ( $_POST['action'] == 'add' && isset($_POST['name']) && $_POST['name'] <> '' ) {
		$item = new Event();
		$item->name = $_POST['name'];
		$item->location = $_POST['location'];
		$item->date = $_POST['aa'] . '-' . $_POST['mm'] . '-' . $_POST['jj'];
		$item->save();
	}

	if ( $_POST['action'] == 'edit' && isset($_POST['name']) && $_POST['name'] <> '' ) {
		$item = Event::getFromIndex($_POST['itemid']);
		$item->name = $_POST['name'];
		$item->location = $_POST['location'];
		$item->date = $_POST['aa'] . '-' . $_POST['mm'] . '-' . $_POST['jj'];
		$item->save();
	}
}

if (isset($_GET['delitem']))
{
Event::delete($_GET['delitem']);
}

All the POST action functions work and the Event class can access $wpdb, but with the last one, which checks for $_GET['delitem'] $wpdb returns an empty value when called in the Event class.

Any ideas what the problem is? Thanks.