Index: modules/comment/comment.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/comment/comment.module,v
retrieving revision 1.888
diff -u -r1.888 comment.module
--- modules/comment/comment.module	10 Aug 2010 00:55:38 -0000	1.888
+++ modules/comment/comment.module	18 Aug 2010 14:39:36 -0000
@@ -839,7 +839,8 @@
     // See comment above. Analysis reveals that this doesn't cost too
     // much. It scales much much better than having the whole comment
     // structure.
-    $query->orderBy('SUBSTRING(c.thread, 1, (LENGTH(c.thread) - 1))', 'ASC');
+    $query->addExpression('SUBSTRING(c.thread, 1, (LENGTH(c.thread) - 1))', 'torder');
+    $query->orderBy('torder', 'ASC');
   }
 
   $query->setCountQuery($count_query);