Activity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@44f72ff0 that was originally added here

Question

You are leaking the dialog. You need to call pDialog.dismiss(); in the onPostExecute() method of the async task. You should also put...

if(pDialog != null)
    pDialog.dismiss();

in your onPause() method of the activity on the main thread. This will make sure the window is not leaked, even if your application loses the foreground while doing some background execution. You should have something like this...

public class Login extends Activity implements View.OnClickListener{

    ProgressDialog pd;

    public void onCreate(Bundle savedInstanceState){

        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
        setContentView(R.layout.login);
        pd = null;
    } 

    @Override
    public void onPause(){

        super.onPause();
        if(pd != null)
            pd.dismiss();
    }

    public void onClick(View v){
        new SendTask().execute("");
    }

    /*
    No networking allowed on the main thread.
    */
    private class SendTask extends AsyncTask<String,String,String>{

        int result;

        @Override
        protected void onPreExecute(){
            pd = ProgressDialog.show(Login.this,"","Retrieving Inbox...", true,false);
        }

        @Override
        protected String doInBackground(String...strings){

            //do networking here
            result = account.prepare();
            return null;
        }

        @Override
        protected void onPostExecute(String unused){

            //check result
            pd.dismiss();
            Intent intent = new Intent(Login.this,NextActivity.class);
            finish();
            startActivity(intent);
        }
     }
}

You are trying to show a dialog window after you are exit from your screen.

Use this in onStop --->

@Override
    protected void onStop() {

        super.onStop();

        if (pDialog != null) {
            pDialog.dismiss();
            pDialog = null;
        }

    }

You have to dismiss the dialog before activity get destroyed

@Override
protected void onDestroy() {
    super.onDestroy();
    if(pDialog!=null && pDialog.isShowing())
        pDialog.dismiss();
}