Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 6385)
+++ wp-includes/pluggable.php	(working copy)
@@ -308,7 +308,7 @@
 
 	$login = get_userdatabylogin($username);
 
-	if ( !$login || ($login->user_login != $username) ) {
+	if ( !$login ) {
 		$error = __('<strong>ERROR</strong>: Invalid username.');
 		return false;
 	}