Index: wp-includes/theme.php
===================================================================
--- wp-includes/theme.php	(revision 21953)
+++ wp-includes/theme.php	(working copy)
@@ -171,7 +171,7 @@
  * @return string
  */
 function get_stylesheet_directory_uri() {
-	$stylesheet = get_stylesheet();
+	$stylesheet = str_replace( '%2F', '/', rawurlencode( get_stylesheet() ) );
 	$theme_root_uri = get_theme_root_uri( $stylesheet );
 	$stylesheet_dir_uri = "$theme_root_uri/$stylesheet";
 
@@ -265,7 +265,7 @@
  * @return string Template directory URI.
  */
 function get_template_directory_uri() {
-	$template = get_template();
+	$template = str_replace( '%2F', '/', rawurlencode( get_template() ) );
 	$theme_root_uri = get_theme_root_uri( $template );
 	$template_dir_uri = "$theme_root_uri/$template";