Index: wp-includes/theme.php
===================================================================
--- wp-includes/theme.php	(revision 56481)
+++ wp-includes/theme.php	(working copy)
@@ -196,6 +196,10 @@
 function get_stylesheet_directory() {
 	global $wp_stylesheet_path;
 
+	if ( function_exists( 'ms_is_switched' ) && ms_is_switched() ) {
+	    $wp_stylesheet_path = null;
+	}
+	
 	if ( null === $wp_stylesheet_path ) {
 		$stylesheet     = get_stylesheet();
 		$theme_root     = get_theme_root( $stylesheet );
@@ -346,6 +350,10 @@
 function get_template_directory() {
 	global $wp_template_path;
 
+	if ( function_exists( 'ms_is_switched' ) && ms_is_switched() ) {
+	    $wp_template_path = null;
+	}
+	
 	if ( null === $wp_template_path ) {
 		$template     = get_template();
 		$theme_root   = get_theme_root( $template );