Index: apachesolr.module
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/apachesolr/apachesolr.module,v
retrieving revision 1.1.2.20
diff -u -r1.1.2.20 apachesolr.module
--- apachesolr.module	20 Jul 2008 10:33:15 -0000	1.1.2.20
+++ apachesolr.module	31 Aug 2008 19:57:16 -0000
@@ -160,7 +172,7 @@
                              'FROM {node} n LEFT JOIN {node_comment_statistics} c ON n.nid = c.nid '.
                              'WHERE n.status = 1 '.
                              '  AND ((GREATEST(n.changed, c.last_comment_timestamp) = %d AND n.nid > %d) OR (n.changed > %d OR c.last_comment_timestamp > %d)) '.
-                             'ORDER BY GREATEST(n.changed, c.last_comment_timestamp) ASC, n.nid ASC', $cron_change, $cron_last, $cron_change, $cron_change, $cron_change, 0, $cron_limit);
+                             'ORDER BY GREATEST(n.changed, IF(c.last_comment_timestamp IS NULL, 0, c.last_comment_timestamp)) ASC, n.nid ASC', $cron_change, $cron_last, $cron_change, $cron_change, $cron_change, 0, $cron_limit);   
     return $result;
   }