Index: src/org/openstreetmap/josm/gui/dialogs/properties/TagEditHelper.java
===================================================================
--- src/org/openstreetmap/josm/gui/dialogs/properties/TagEditHelper.java	(revision 7609)
+++ src/org/openstreetmap/josm/gui/dialogs/properties/TagEditHelper.java	(working copy)
@@ -504,6 +504,7 @@
                    Collections.sort(valueList, comparator);
 
                    values.setPossibleACItems(valueList);
+                   values.getEditor().selectAll();
                    objKey=key;
                }
            };