Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.478
diff -u -r1.478 form.inc
--- includes/form.inc	17 Jul 2010 18:52:39 -0000	1.478
+++ includes/form.inc	23 Jul 2010 13:30:52 -0000
@@ -2803,7 +2803,7 @@
             '#title' => '',
             '#return_value' => $key,
             '#default_value' => isset($value[$key]) ? $key : NULL,
-            '#attributes' => $element['#attributes'],
+            '#attributes' => $element['#attributes'] + array('title' => t('Select this row')),
           );
         }
         else {
@@ -2815,7 +2815,7 @@
             '#title' => '',
             '#return_value' => $key,
             '#default_value' => ($element['#default_value'] == $key) ? $key : NULL,
-            '#attributes' => $element['#attributes'],
+            '#attributes' => $element['#attributes'] + array('title' => t('Select this row')),
             '#parents' => $element['#parents'],
             '#id' => drupal_html_id('edit-' . implode('-', $parents_for_id)),
             '#ajax' => isset($element['#ajax']) ? $element['#ajax'] : NULL,