Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.426
diff -u -p -r1.426 form.inc
--- includes/form.inc	8 Jan 2010 06:36:34 -0000	1.426
@@ -1718,9 +1719,10 @@ function form_type_select_value($element
  *   for this element. Return nothing to use the default.
  */
 function form_type_textfield_value($element, $input = FALSE) {
-  if ($input !== FALSE) {
-    // Equate $input to the form value to ensure it's marked for
-    // validation.
+  // If something is submitted, return a string with newlines stripped. If
+  // nothing is submitted (not even an empty string), return NULL so that the
+  // element's default value is used.
+  if ($input !== FALSE && isset($input)) {
     return str_replace(array("\r", "\n"), '', $input);
   }
 }