Index: wp-includes/theme.php
===================================================================
--- wp-includes/theme.php	(revision 21088)
+++ wp-includes/theme.php	(working copy)
@@ -395,6 +395,8 @@
 				foreach ( $sub_dirs as $sub_dir ) {
 					if ( ! is_dir( $theme_root . '/' . $dir ) || $dir[0] == '.' || $dir == 'CVS' )
 						continue;
+					if ( ! is_dir( $theme_root . '/' . $dir . '/' . $sub_dir ) )
+						continue;
 					if ( ! file_exists( $theme_root . '/' . $dir . '/' . $sub_dir . '/style.css' ) )
 						continue;
 					$found_themes[ $dir . '/' . $sub_dir ] = array(
@@ -1685,4 +1687,4 @@
 		}());
 	</script>
 	<?php
-}
\ No newline at end of file
+}