Index: wp-includes/kses.php
===================================================================
--- wp-includes/kses.php	(revision 12320)
+++ wp-includes/kses.php	(working copy)
@@ -948,7 +948,7 @@
 function wp_kses_normalize_entities($string) {
 	# Disarm all entities by converting & to &
 
-	$string = str_replace('&', '&', $string);
+	$string = str_replace('&', '%%ampplaceholder%%', $string);
 
 	# Change back the allowed entities in our entity whitelist
 
@@ -956,6 +956,8 @@
 	$string = preg_replace_callback('/&#0*([0-9]{1,5});/', 'wp_kses_normalize_entities2', $string);
 	$string = preg_replace_callback('/&#([Xx])0*(([0-9A-Fa-f]{2}){1,2});/', 'wp_kses_normalize_entities3', $string);
 
+	$string = str_replace('%%ampplaceholder%%', '&', $string);
+
 	return $string;
 }