Index: modules/node/node.pages.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/node/node.pages.inc,v
retrieving revision 1.136
diff -u -p -r1.136 node.pages.inc
--- modules/node/node.pages.inc	26 Nov 2010 19:23:01 -0000	1.136
+++ modules/node/node.pages.inc	13 Jan 2011 18:19:26 -0000
@@ -380,9 +380,12 @@ function theme_node_preview($variables) 
 
   $preview_trimmed_version = FALSE;
 
+  // When calling node_view() on a previewed node, we must make sure to clone
+  // the node as template_preprocess_node() does modify the node object which
+  // could affect data when the node is saved.
   $elements = node_view(clone $node, 'teaser');
   $trimmed = drupal_render($elements);
-  $elements = node_view($node, 'full');
+  $elements = node_view(clone $node, 'full');
   $full = drupal_render($elements);
 
   // Do we need to preview trimmed version of post as well as full version?