Commenting this out for now for performance reasons, should be fixed soon!

See MDL-8385

lib/accesslib.php

@@ -72,7 +72,7 @@ function load_guest_role($context=NULL) {
         }
     }
 
-    $searchcontexts = get_child_contexts($context);
+    $searchcontexts = array();  // get_child_contexts($context);   SEE MDL-8385
     array_push($searchcontexts, $context->id);
 
     foreach ($searchcontexts as $scid) {
@@ -3418,4 +3418,4 @@ function user_has_role_assignment($userid, $roleid, $contextid=0) {
         return record_exists('role_assignments', 'userid', $userid, 'roleid', $roleid);
     }
 }
-?>
+?>