Backed out of change to unmapAllElements
diff --git a/bundles/org.eclipse.ui/Eclipse JFace/org/eclipse/jface/viewers/StructuredViewer.java b/bundles/org.eclipse.ui/Eclipse JFace/org/eclipse/jface/viewers/StructuredViewer.java
index 30363e2..1dc5bdb 100644
--- a/bundles/org.eclipse.ui/Eclipse JFace/org/eclipse/jface/viewers/StructuredViewer.java
+++ b/bundles/org.eclipse.ui/Eclipse JFace/org/eclipse/jface/viewers/StructuredViewer.java
@@ -832,11 +832,6 @@
  */

 protected void unmapAllElements() {

 	if (elementMap != null) {

-		// need to clear the Item->element association as well as the element->Item association

-		for (Iterator i = elementMap.values().iterator(); i.hasNext();) {

-			Widget w = (Widget) i.next();

-			w.setData(null);

-		}

 		elementMap = new HashMap();

 	}

 }