Index: includes/node_widget.form.inc
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/node_widget/includes/node_widget.form.inc,v
retrieving revision 1.2
diff -u -p -r1.2 node_widget.form.inc
--- includes/node_widget.form.inc	10 Feb 2010 13:21:40 -0000	1.2
+++ includes/node_widget.form.inc	12 Feb 2010 16:31:12 -0000
@@ -116,12 +116,27 @@ function node_widget_form_alter(&$form, 
  * @see: node_widget_widget()
  */
 function node_widget_node_form_after_build(&$form, &$form_state) {
+  $groups = (module_exists('fieldgroup') ? fieldgroup_groups($form['type']['#value']) : array());
   foreach ($form['#field_info'] as $field_name => $field) {
     if ($field['type'] == 'nodereference' && $field['widget']['type'] == 'node_widget_node_form') {
       // Disable element validation, ti will take place in node_widget_element_validate()
-      foreach ($form[$field_name] as $key => $_field) {
-        if (is_int($key)) {
-          _node_widget_toggle_validation($form[$field_name][$key]['node_widget'], FALSE);
+      if (isset($form[$field_name])) {
+        foreach ($form[$field_name] as $key => $_field) {
+          if (is_int($key)) {
+            _node_widget_toggle_validation($form[$field_name][$key]['node_widget'], FALSE);
+          }
+        }
+      }
+      elseif (module_exists('fieldgroup')) {
+        // Guess the field is "hidden" in a fieldgroup.
+        foreach ($groups as $groupkey => $group) {
+          if (isset($form[$groupkey][$field_name])) {
+            foreach ($form[$groupkey][$field_name] as $key => $_field) {
+              if (is_int($key)) {
+                _node_widget_toggle_validation($form[$groupkey][$field_name][$key]['node_widget'], FALSE);
+              }
+            }
+          }
         }
       }
     }