User.Identity.Name is blank ASP.NET
<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="http://stackoverflow.com/questions/7839567/why-does-httpcontext-current-user-identity-name-return-blank">Why does HttpContext.Current.User.Identity.Name return blank</a>  </p>
</blockquote>



<p>This website has been setup for a very long time and last week all of a sudden it started giving errors. After much debugging I found that the problem was User.Identity.Name. Its returning blank value</p>

<p>We are using Windows Authorization </p>

<p>here is the web.config code</p>

<pre><code>&lt;authentication mode="Windows"/&gt;
&lt;identity impersonate="true" /&gt;

&lt;authorization&gt;
  &lt;allow users="*"/&gt;
&lt;/authorization&gt;
</code></pre>

<p>I also tried reverting all my code but the variable is still returning blank</p>

<p>How can I debug this issue?</p>
