Index: misc/tableheader.js
===================================================================
RCS file: /cvs/drupal/drupal/misc/tableheader.js,v
retrieving revision 1.10
diff -u -p -r1.10 tableheader.js
--- misc/tableheader.js	9 Jan 2008 09:56:39 -0000	1.10
+++ misc/tableheader.js	10 Jan 2008 15:00:13 -0000
@@ -16,6 +16,13 @@ Drupal.behaviors.tableHeader = function 
       visibility: 'hidden',
       top: '0px'
     });
+
+    // Sets an id for cloned table header.
+    var headerID = headerClone.attr('id');
+    if (headerClone.attr('id') != '') {
+      headerClone.removeAttr('id').attr('id', headerID + '-header');
+    }
+
     // Everything except thead must be removed. See theme_table().
     $('tbody', headerClone).remove();
     $('caption', headerClone).remove();