Index: modules/forum/forum.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/forum/forum.module,v
retrieving revision 1.583
diff -u -p -r1.583 forum.module
--- modules/forum/forum.module	28 Jan 2011 08:02:37 -0000	1.583
+++ modules/forum/forum.module	30 Jan 2011 16:38:41 -0000
@@ -695,6 +695,11 @@ function forum_block_view_pre_render($el
     $elements['forum_list'] = $node_title_list;
     $elements['forum_more'] = array('#theme' => 'more_link', '#url' => 'forum', '#title' => t('Read the latest forum topics.'));
   }
+  else {
+    $elements['forum_list'] = array(
+      '#markup' => t('No content available.'),
+    );
+  }
   return $elements;
 }