Mollom captch disappear after using hook form alter for validation I have altered Request new password form  field label 

function useredit_form_user_pass_alter(&amp;$form, &amp;$form_state, $form_id) {
  $form['name']['#title']='Username';
  $form['#validate'] = array('useredit_user_pass_validation');
}

function useredit_user_pass_validation($form, &amp;$form_state) {

  $name = trim($form_state['values']['name']);
  if(preg_match("/^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/",$name))
  {
     form_set_error('parent_field_email', t('Please enter valid username.'));
  }
  # try to load by name.
  $users = user_load_multiple(array(), array('name' =&gt; $name, 'status' =&gt; '1'));
  $account = reset($users);

  if (isset($account-&gt;uid)) {
    form_set_value(array('#parents' =&gt; array('account')), $account, $form_state);
  }else{
    form_set_error('name', t('Sorry, %name is not recognized as a user name.', array('%name' =&gt; $name)));
  }
  }


form get's altered and validation works but captch image gets disappear. How to resolve this ?
I have done below changed above code:

$form['#validate'] = array('useredit_user_pass_validation');


by 

$form['#validate'][] = 'useredit_user_pass_validation';


And it's works !