'Illegal choice' error while submitting/validating selectbox shown with AJAX

I'm making a module where the content type and fields are created by install. Now i want to make one of those fields only to show up when an option is selected. I did this with AJAX, in some way I can't make it work with the field as defined in the module.install file. I have a radio button selector for two options. When selecting the first option there should show up a selectbox with a list of nodes to select. When selecting the second option two textfields should be shown instead. When I try to add content of this type I get the error message (when changing the value from the radio buttons):

An illegal choice has been detected. Please contact the site administrator.

Can someone give me some advice to make this work? Thanks in advance!

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Here is my code from the install file:

function _concert_installed_fields() {
  $t = get_t();
  return array(
      // other fields left out
    'venue_node' => array(
     'field_name' => 'venue_node',
     'label' => 'Select a venue from the list',
     'type' => 'list_integer',
     'cardinality' => '1',
     'foreign keys' => array(),
     'indexes' => array(
       'value' => array(
        0 => 'value',
       ),
      ),
     'module' => 'list',
     'settings' => array(
      'allowed_values_function' => '_concert_content_type_venue_options_list',
      ),
    ),
    'venue_radio' => array(
     'field_name' => 'venue_radio',
     'cardinality' => 1,
     'type' => 'list_boolean',
    )
  );

From my .module file:

function concert_form_alter(&$form, &$form_state, $form_id) {
if($form_id == "concert_node_form") {
$form['venue_radio'] = array(
	  '#title' => t("Choose a venue from the database or add one manually"),
	  '#type' => 'radios',
	  '#options' => array(0 => t('Add a venue from the database.'),
						  1 => t('Add a venue manually.'),),
	  '#ajax' => array(
		'callback' => 'concert_venue_callback',
		'wrapper' => 'venue_select',
		'effect' => 'fade',
	  ),
	);

$form['venue_select'] = array(
	  '#prefix' => '<div id = "venue_select">',
	  '#suffix' => '</div>',
	  '#type' => 'fieldset',
	);
if (!empty($form_state['values']['venue_radio']) && $form_state['values']['venue_radio'] == "1") {
	  $form['venue_node']['#type'] = 'hidden';
	  
	  $form['venue_select']['location'] = array(
		'#type' => 'textfield',
		'#title' => t('location'),
		
	  );
	  $form['venue_select']['venue_city'] = array(
		'#type' => 'textfield',
		'#title'=> t('city'),
	  );
	}
	
	else {
 $form['venue_select']['venue_node'] = array(
		'#type' => 'select',
		'#options' => _concert_content_type_venue_options_list(),
		'#title' => t('venue node select'),
		'#default_value' => '466', // node id is select value
	  );
if (!empty($form_state['values']['venue_node']))
    $form['concert_venue_node']['und']['#default_value'] = $form_state['values']['venue_node']; 
}

function concert_venue_callback($form, $form_state) {
  return $form['venue_select'];
}

The options from the selectbox are populated by a function in a file accessable for both the .install and the .module file:

function _concert_content_type_venue_options_list() {
 
 $results = db_select('node', 'n')
    ->fields('n', array('nid', 'title'))
    ->condition('n.status', 1)
    ->condition('n.type', 'venue')
    ->execute();
    
 $options = array();
 foreach ($results as $node) {
  $options[$node->nid] = $node->title;
 }
 return $options;
}