Why am I getting Http/1.1 400 Bad request?

Here is a snippet of my code. I am trying to login to the website using HTTPOST.

I keep getting "400 Bad Request" I have tried various combinations. I tried passing username/password as header instead of NameValuePair. But same result. Is there something I am missing?

HttpClient httpclient = new DefaultHttpClient();
        
HttpPost post = new HttpPost("https://identi.ca/main/login");
    

List <NameValuePair> nvps = new ArrayList <NameValuePair>();
nvps.add(new BasicNameValuePair("nickname", u));
nvps.add(new BasicNameValuePair("password", p));
nvps.add(new BasicNameValuePair("submit", "Login"));

post.setEntity(new UrlEncodedFormEntity(nvps, HTTP.UTF_8));

HttpResponse response = httpclient.execute(post);
HttpEntity entity = response.getEntity();

Log.i("Login form POST result: ", response.getStatusLine().toString());
        

Thanks for help.