--- user_creator.module	2010-06-03 14:00:00.000000000 -0400
+++ user_creator.new.module	2010-06-03 14:03:33.000000000 -0400
@@ -290,7 +290,7 @@ function user_creator_register() {
     unset($form['account']);
   }
   else {
-    $form = array_merge($form, $extra);
+    $form = array_merge_recursive($form, $extra);
   }
 
   if (variable_get('configurable_timezones', 1)) {