Fixes bug mentioned here: http://drupal.org/comment/reply/300084?page=1#comment-3067620

diff -Nurp ../cck.orig/modules/content_multigroup/content_multigroup.admin.inc ./modules/content_multigroup/content_multigroup.admin.inc
--- ../cck.orig/modules/content_multigroup/content_multigroup.admin.inc	2010-06-10 10:28:31.000000000 -0500
+++ ./modules/content_multigroup/content_multigroup.admin.inc	2010-06-10 10:29:08.000000000 -0500
@@ -355,22 +355,13 @@ function content_multigroup_display_over
 
       // We have some numeric keys here, so we can't use array_merge.
       foreach ($values as $k => $v) {
-        $group['settings']['multigroup']['subgroup'][$k] = $v;
+        $form_state['values'][$group_name]['settings']['multigroup']['subgroup'][$k] = $v;
       }
 
-      // Update the group information in the database. Note that
-      // 'fieldgroup_data' in cache tables are also cleared here,
-      // but we need to reset static caches of fieldgroup_groups().
-      fieldgroup_save_group($form['#type_name'], $group);
-      $reset_cache = TRUE;
-
       // Remove the subgroup from $form_state.
       unset($form_state['values'][$key]);
     }
   }
-  if ($reset_cache) {
-    fieldgroup_groups('', FALSE, TRUE);
-  }
 }
 
 /**
diff -Nurp ../cck.orig/modules/fieldgroup/fieldgroup.module ./modules/fieldgroup/fieldgroup.module
--- ../cck.orig/modules/fieldgroup/fieldgroup.module	2010-06-10 10:28:31.000000000 -0500
+++ ./modules/fieldgroup/fieldgroup.module	2010-06-10 10:29:08.000000000 -0500
@@ -519,6 +519,18 @@ function fieldgroup_display_overview_for
   foreach ($form_values as $key => $values) {
     if (in_array($key, $form['#groups'])) {
       $group = $groups[$key];
+      // Multigroup data (namely, subgroup data) ends up in the settings array as well
+      // Prevent this data from ending up inside of ['settings']['display']
+      if (is_array($values['settings']) && array_key_exists('multigroup', $values['settings'])){
+        if (is_array($group['settings']['multigroup'])){
+          foreach ($values['settings']['multigroup'] as $mg_key => $mg_values){
+            $group['settings']['multigroup'][$mg_key] = $values['settings']['multigroup'][$mg_key];
+          }
+        } else {
+          $group['settings']['multigroup'] = $values['settings']['multigroup'];
+        }
+        unset($values['settings']['multigroup']);
+      }
       // We have some numeric keys here, so we can't use array_merge.
       $group['settings']['display'] = $values + $group['settings']['display'];
       fieldgroup_save_group($form['#type_name'], $group);