Index: modules/forum/forum.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/forum/forum.module,v
retrieving revision 1.565
diff -u -p -r1.565 forum.module
--- modules/forum/forum.module	28 Apr 2010 05:54:55 -0000	1.565
+++ modules/forum/forum.module	30 Apr 2010 19:37:25 -0000
@@ -167,9 +167,9 @@ function forum_menu() {
 function forum_menu_local_tasks_alter(&$data, $router_item, $root_path) {
   global $user;
 
-  // Add action link to 'node/add/forum' on 'forum' page.
-  if ($root_path == 'forum') {
-    $tid = (isset($router_item['page_arguments'][0]) ? $router_item['page_arguments'][0] : 0);
+  // Add action link to 'node/add/forum' on 'forum' page and sub-pages.
+  if (substr($root_path, 0, 5) == 'forum') {
+    $tid = (isset($router_item['page_arguments'][0]) ? $router_item['page_arguments'][0]->tid : 0);
     $forum_term = forum_forum_load($tid);
     if ($forum_term) {
       $vid = variable_get('forum_nav_vocabulary', 0);