Index: modules/system/system.admin.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.admin.inc,v
retrieving revision 1.309
diff -u -p -r1.309 system.admin.inc
--- modules/system/system.admin.inc	24 Sep 2010 21:36:22 -0000	1.309
+++ modules/system/system.admin.inc	27 Sep 2010 21:45:05 -0000
@@ -723,7 +723,7 @@ function system_theme_settings_validate(
  *   the path could not be validated.
  */
 function _system_theme_settings_validate_path($path) {
-  if (drupal_realpath($path)) {
+  if (drupal_realpath($path) && file_exists(drupal_realpath($path))) {
     // The path is relative to the Drupal root, or is a valid URI.
     return $path;
   }