Index: wp-includes/canonical.php
===================================================================
--- wp-includes/canonical.php	(revision 15434)
+++ wp-includes/canonical.php	(working copy)
@@ -341,7 +341,7 @@
 			$redirect_url .= '?' . $redirect['query'];
 	}
 
-	if ( !$redirect_url || $redirect_url == $requested_url )
+	if ( !$redirect_url || ( $redirect_url == $requested_url ) || ( $redirect_url == strtolower($requested_url) ) )
 		return false;
 
 	// Note that you can use the "redirect_canonical" filter to cancel a canonical redirect for whatever reason by returning FALSE