Index: cck_blocks.module
===================================================================
--- cck_blocks.module	(revision 134)
+++ cck_blocks.module	(working copy)
@@ -100,7 +100,7 @@
         // cycle through all content data arrays looking for cck groups
         // the cck_field may be within a group
         foreach ($built_nodes[$nid]->content as $key => $data) {
-          if ((strpos($key, 'group_') == 0) && isset($data['group'][$delta])) {
+          if (is_array($data) && (strpos($key, 'group_') == 0) && isset($data['group'][$delta])) {
             // yay it's a group
             $cck_field_data = $data['group'][$delta];
           }