Index: includes/bootstrap.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/bootstrap.inc,v
retrieving revision 1.206
diff -u -p -r1.206 bootstrap.inc
--- includes/bootstrap.inc	10 Jan 2008 22:47:17 -0000	1.206
+++ includes/bootstrap.inc	11 Feb 2008 14:38:50 -0000
@@ -494,10 +494,18 @@ function variable_del($name) {
  *
  * Note: we do not serve cached pages when status messages are waiting (from
  * a redirected form submission which was completed).
+ *
+ * @param $status_only
+ *   When set to TRUE, retrieve the status of the page cache only
+ *   (whether it was started in this request or not).
  */
-function page_get_cache() {
+function page_get_cache($status_only = FALSE) {
+  static $status = FALSE;
   global $user, $base_root;
 
+  if ($status_only) {
+    return $status;
+  }
   $cache = NULL;
 
   if (!$user->uid && $_SERVER['REQUEST_METHOD'] == 'GET' && count(drupal_set_message()) == 0) {
@@ -505,6 +513,7 @@ function page_get_cache() {
 
     if (empty($cache)) {
       ob_start();
+      $status = TRUE;
     }
   }
 
Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.756
diff -u -p -r1.756 common.inc
--- includes/common.inc	30 Jan 2008 23:07:41 -0000	1.756
+++ includes/common.inc	11 Feb 2008 14:38:54 -0000
@@ -2476,7 +2476,7 @@ function _drupal_bootstrap_full() {
 function page_set_cache() {
   global $user, $base_root;
 
-  if (!$user->uid && $_SERVER['REQUEST_METHOD'] == 'GET' && count(drupal_get_messages(NULL, FALSE)) == 0) {
+  if (!$user->uid && $_SERVER['REQUEST_METHOD'] == 'GET' && page_get_cache(TRUE)) {
     // This will fail in some cases, see page_get_cache() for the explanation.
     if ($data = ob_get_contents()) {
       $cache = TRUE;