I'm experiencing the same. I have also noticed that the list of the context menus on the left hand side lists both of the context menus I have created as RadTreeViewContextMenu and not the IDs that I have assigned to the contextmenus.
Renaming the IDs back to RadTreeViewContextMenu1 and RadTreeViewContextMenu2 does not make a difference.
I do have two treeview controls on the page if that makes a difference.
I am using VWD2008 Express.