Index: wp-admin/includes/ms.php
===================================================================
--- wp-admin/includes/ms.php	(revision 16734)
+++ wp-admin/includes/ms.php	(working copy)
@@ -70,7 +70,7 @@
 	// Remove users from this blog.
 	if ( ! empty( $users ) ) {
 		foreach ( $users as $user ) {
-			remove_user_from_blog( $user->user_id, $blog_id) ;
+			remove_user_from_blog( $user->id, $blog_id) ;
 		}
 	}