? system.admin.276615.patch
Index: modules/system/system.admin.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.admin.inc,v
retrieving revision 1.154
diff -u -p -r1.154 system.admin.inc
--- modules/system/system.admin.inc	6 Jun 2009 16:05:27 -0000	1.154
+++ modules/system/system.admin.inc	7 Jun 2009 17:58:59 -0000
@@ -139,7 +139,6 @@ function system_settings_overview() {
  * @see system_themes_form_submit()
  */
 function system_themes_form() {
-  drupal_clear_css_cache();
 
   $themes = system_get_theme_data();
   uasort($themes, 'system_sort_modules_by_info_name');
@@ -240,6 +239,7 @@ 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();