? system.admin.inc.276615.patch
Index: modules/system/system.admin.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.admin.inc,v
retrieving revision 1.150
diff -u -p -r1.150 system.admin.inc
--- modules/system/system.admin.inc	25 May 2009 18:22:30 -0000	1.150
+++ modules/system/system.admin.inc	28 May 2009 21:26:22 -0000
@@ -139,8 +139,6 @@ function system_settings_overview() {
  * @see system_themes_form_submit()
  */
 function system_themes_form() {
-  drupal_clear_css_cache();
-
   $themes = system_theme_data();
   uasort($themes, 'system_sort_modules_by_info_name');
 
@@ -240,6 +238,7 @@ function system_themes_form() {
  * Process system_themes_form form submissions.
  */
 function system_themes_form_submit($form, &$form_state) {
+  drupal_clear_css_cache();
 
   // Store list of previously enabled themes and disable all themes
   $old_theme_list = $new_theme_list = array();