asp.net Problems with login : login failed for user NT Authority\Anonymous Logon
<p>Im getting the following error when I try to login to web page with a valid username and password:</p>

<blockquote>
  <p>Oops. The error: Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'.</p>
</blockquote>

<p>This is my web.config :</p>

<pre><code>&lt;configuration&gt;
  &lt;system.web&gt;
    &lt;customErrors mode="Off"/&gt;
    &lt;authentication mode="Forms"&gt;
      &lt;forms name=".ASPXFORUM" loginUrl="login.aspx" protection="All" 
                                                    timeout="30" path="/" /&gt;
    &lt;/authentication&gt;
    &lt;authorization&gt;
      &lt;deny users="?" /&gt;
    &lt;/authorization&gt;
  &lt;/system.web&gt;
&lt;/configuration&gt;
</code></pre>

<p>Anyone know what this error mean?</p>
