Index: wp-includes/theme.php
===================================================================
--- wp-includes/theme.php	(revision 20233)
+++ wp-includes/theme.php	(working copy)
@@ -50,7 +50,7 @@
 	if ( is_multisite() && null !== $args['allowed'] ) {
 		$allowed = $args['allowed'];
 		if ( 'network' === $allowed )
-			$theme_directories = array_intersect_key( $theme_directories, WP_Theme::get_allowed_on_network( $args['blog_id'] ) );
+			$theme_directories = array_intersect_key( $theme_directories, WP_Theme::get_allowed_on_network() );
 		elseif ( 'site' === $allowed )
 			$theme_directories = array_intersect_key( $theme_directories, WP_Theme::get_allowed_on_site( $args['blog_id'] ) );
 		elseif ( $allowed )
@@ -62,10 +62,7 @@
 	$themes = array();
 
 	foreach ( $theme_directories as $theme => $theme_root ) {
-		if ( isset( $_themes[ $theme ] ) )
-			$themes[ $theme ] = $_themes[ $theme ];
-		else
-			$themes[ $theme ] = $_themes[ $theme ] = new WP_Theme( $theme, $theme_root['theme_root'] );
+		$themes[ $theme ] = new WP_Theme( $theme, $theme_root['theme_root'] );
 	}
 
 	if ( null !== $args['errors'] ) {