Index: modules/system/system.install
===================================================================
RCS file: /Users/wright/drupal/local_repo/drupal/modules/system/system.install,v
retrieving revision 1.528
diff -u -p -r1.528 system.install
--- modules/system/system.install	30 Nov 2010 01:05:24 -0000	1.528
+++ modules/system/system.install	3 Dec 2010 17:20:58 -0000
@@ -2934,8 +2934,11 @@ function system_update_7065() {
  * Migrate the 'file_directory_temp' variable.
  */
 function system_update_7066() {
-  $d6_file_directory_temp = variable_get('file_directory_temp', file_directory_temp());
-  variable_set('file_temporary_path', $d6_file_directory_temp);
+  $d7_temp_path = variable_get('file_temporary_path', NULL);
+  $d6_temp_path = variable_get('file_directory_temp', NULL);
+  if (empty($d7_temp_path) && !empty($d6_temp_path)) {
+    variable_set('file_temporary_path', $d6_temp_path);
+  }
   variable_del('file_directory_temp');
 }