RadTreeView does not handle the Enter key since Q3 2011. Instead it uses CommandBindings:
Enter key toggles the expand/collapse state of the selected item. However, if you have particular issue with the enter key functionality, please provide some further details about it in a new support thread.
Do you need help with upgrading your AJAX, WPF or WinForms project? Check the Telerik API Analyzer
and share your thoughts.