Index: modules/update/update.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/update/update.module,v
retrieving revision 1.22
diff -u -p -r1.22 update.module
--- modules/update/update.module	6 Sep 2008 08:36:22 -0000	1.22
+++ modules/update/update.module	12 Sep 2008 07:32:10 -0000
@@ -276,7 +276,9 @@ function _update_requirement_check($proj
 function update_cron() {
   $frequency = variable_get('update_check_frequency', 1);
   $interval = 60 * 60 * 24 * $frequency;
-  if ($_SERVER['REQUEST_TIME'] - variable_get('update_last_check', 0) > $interval) {
+  // Cron should check for updates if there is no update data cached or if the configured
+  // update interval has elapsed.
+  if (!cache_get('update_info', 'cache_update') || $_SERVER['REQUEST_TIME'] - variable_get('update_last_check', 0) > $interval) {
     update_refresh();
     _update_cron_notify();
   }