Twitter bootstrap + asp.net masterpages, navbar active item doesn't works for dropdown lists

Question

This solution has worked wonderfully for me except for one glitch. It doesn't works for dropdown menu. (I'm using Bootstrap v 2.1.1)

Like this,

<li class="dropdown">
      <a href="#" class="dropdown-toggle" data-toggle="dropdown">
           Account <b class="caret"></b>
      </a>
      <ul class="dropdown-menu">
           <li>
               <a href="Login.aspx">Login</a>
           </li>
           <li>
               <a href="xxx">Register</a>
           </li>
      </ul>
</li>

Shows something like this....(Attached below)
As you can see for the dropdown no menu title available and it is always selected.