I think that the Q1 2009 release changed the way many of the RadControls for Silverlight were styled, so I expect you will need to update your custom themes. To do that, you have a couple of options:
- The simplest approach is to open the RadControls in Blend > Select a control > Click the "Edit control template..." menu action > and then edit a copy of the default template. This will create a copy of the default XAML template that you can start editing right away.
- If you want to edit one of the non-default themes, a little more work is required. The tutorial for editing the non-defualt themes is not yet posted, but if you'd like an early draft, simply open a support ticket and the support team can send it to you.
The good news is that all RadControls in Q1 are fully Blend 2 compatibile, which means you can edit any of their templates directly in Blend. Hopefully that will help you get started with your XAML customizations.
Hope that helps-