Index: session.php
===================================================================
--- session.php	(revision 13782)
+++ session.php	(working copy)
@@ -451,7 +451,11 @@
 
 		$user_id = $session->RecallVar('user_id');
 
-		if ($user_id != USER_GUEST) {
+		if ($user_id == USER_GUEST || $user_id === false) {
+			// -2 (when not logged in), false (when after u:OnLogout event)
+			$session->RemoveVar($var_name);
+		}
+		else {
 			$sql = 'DELETE FROM '.TABLE_PREFIX.'PersistantSessionData
 					WHERE PortalUserId = '.$user_id.' AND VariableName = '.$this->Conn->qstr($var_name);
 			$this->Conn->Query($sql);