--- grc/gui/BlockTreeWindow.py	2015-10-31 12:33:23.000000000 -0500
+++ grc/gui/BlockTreeWindow.py.new	2015-11-12 10:15:51.272620638 -0600
@@ -125,7 +125,8 @@
         if treestore is None: treestore = self.treestore
         if categories is None: categories = self._categories
 
-        if isinstance(category, str): category = category.split('/')
+#        if isinstance(category, str): category = category.split('/')
+        if isinstance(category, basestring): category = category.split('/')
         category = tuple(filter(lambda x: x, category)) #tuple is hashable
         #add category and all sub categories
         for i, cat_name in enumerate(category):