Index: captcha.module
===================================================================
--- captcha.module	(revision 1764)
+++ captcha.module	(working copy)
@@ -568,13 +568,13 @@
     return;
   }
   // Get answer and preprocess if needed
-  $captcha_response = $form_values['#post']['captcha_response'];
+  $captcha_response = ($form_values['#tree'] ? $form_values['#post']['captcha']['captcha_response'] : $form_values['#post']['captcha_response']);
   $validationdata = $form_values['validationdata']['#value'];
   if ($validationdata['preprocess']) {
     $captcha_response = module_invoke($validationdata['module'], 'captcha', 'preprocess', $validationdata['type'], $captcha_response);
   }
   $form_id = $validationdata['form_id'];
-  $captcha_token = $form_values['#post']['captcha_token'];
+  $captcha_token = ($form_values['#tree'] ? $form_values['#post']['captcha']['captcha_token'] : $form_values['#post']['captcha_token']);
   // Check if captcha_token exists
   if (!isset($_SESSION['captcha'][$form_id][$captcha_token])) {
     form_set_error('captcha_token', t('Invalid CAPTCHA token.'));