Index: wp-includes/classes.php
===================================================================
--- wp-includes/classes.php	(revision 4847)
+++ wp-includes/classes.php	(working copy)
@@ -1525,7 +1525,7 @@
 			// front.  For path info requests, this leaves us with the requesting
 			// filename, if any.  For 404 requests, this leaves us with the
 			// requested permalink.	
-			$req_uri = str_replace($pathinfo, '', $req_uri);
+			$req_uri = str_replace($pathinfo, '', urldecode($req_uri));
 			$req_uri = trim($req_uri, '/');
 			$req_uri = preg_replace("|^$home_path|", '', $req_uri);
 			$req_uri = trim($req_uri, '/');