Thank you for writing and pointing this issue out. The RefreshText method does not work because it is not implemented in the RadBreadCrumb. I have fixed the bread crumb and now it can be refreshed by calling UpdateBreadCrumb(RadTreeNode n). The argument should, in your case, be the SelectedNode of the RadTreeView. This fix will be included in the Q1 2009 SP1, which will be available in about a month.
Please write back if you have other questions.
the Telerik team