Microsoft.SharePoint.WebPartPages.WebPart SPCalendarView and Ribbon

I have created a custom calendar based off the SPCalendarView using the Microsoft.SharePoint.WebPartPages.WebPart.  I have replaced the default webpart on Calendar list with my webpart.  Everything works beautifully, but I do not get the standard Ribbon groups "Calendar Tools" and "List Tools" .  I have tried using the

ribbon.MakeTabAvailable("Ribbon.Calendar.Calendar");

 ribbon.MakeContextualGroupInitiallyVisible("Ribbon.Calendar", string.Empty);

which shows the group, but as soon as you click on it, it tries to load then disappears. And ideas?