Plugin options not being saved

I am writing my first plugin, I think am doing alright but whenever I try to save the options I get the following error

Your attempt to edit your settings has failed.

Below please find the code of the interface part of the plugin

<div class="wrap">
  <h2>Display Author Avatar Options</h2>

  <form method="post" action="options.php">
      <?php wp_nonce_field('update_options'); ?>

      <table class="form-table">
          <tr valign="top">
          <th scope="row">Style</th>
          <td><input type="text" name="daao_style" value="<?php echo get_option('daao_style'); ?>" size="75" /></td>
          </tr>
      </table>

      <input type="hidden" name="action" value="update" />
      <input type="hidden" name="page_options" value="daao_style" />

      <p class="submit">
      <input type="submit" class="button-primary" value="<?php _e('Save Changes') ?>" />
      </p>

  </form>
</div>

Any help to resolve this issue will highly be appreciated.
TIA