Index: modules/node/node.pages.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/node/node.pages.inc,v
retrieving revision 1.60
diff -u -p -r1.60 node.pages.inc
--- modules/node/node.pages.inc	15 Apr 2009 13:28:08 -0000	1.60
+++ modules/node/node.pages.inc	25 Apr 2009 17:00:23 -0000
@@ -119,10 +119,10 @@ function node_form(&$form_state, $node) 
       $node->$key = NULL;
     }
   }
-  if (!isset($form_state['node_preview'])) {
+  if (!isset($form_state['node_preview']) && !$form_state['submitted']) {
     node_object_prepare($node);
   }
-  else {
+  else if (isset($form_state['node_preview'])) {
     $node->build_mode = NODE_BUILD_PREVIEW;
   }