title: mongoe's findOne method nether executes nor fails
body: <p>I'm trying to retrieve data from mongodb through nodejs mnogdb-native driver. <code>mongod</code>console indicates that connection succeed. Unfortunately, after retrieving collection and logging message 'before findOne' to the console nothing happened. It's looks like the<code>findOne</code> method never returns.</p>
  
  <pre><code>var mongo = require('mongodb'),
      config = require('./config');
  
  var UserProvider = function() {
      this.db = new mongo.Db('chatbox', 
          new mongo.Server(config.mongoServer, config.mongoPort, {auto_reconnect: true}), {});
      this.db.open(function() {});
  };
  
  UserProvider.prototype.getCollection = function(callback) {
      this.db.collection('users', function(error, collection) {
      if (error) {
          callback(error);
      }
      else {
          callback(null, collection);
      }
      });
  };
  
  UserProvider.prototype.validateUser = function(username, password, callback) {
      this.getCollection(function(error, collection) {
          if (error) {
              console.log('error');
              callback(error);
          }
          else {
              console.log('before findOne');
              collection.findOne({login: username, password: password}, function(error, item){
                  console.log('done');
                  if (error) {
                      callback(error);
                  }
                  else {
                      callback(null, item != null);
                  }
              });
          }   
      });
  };
  
  module.exports = UserProvider;
  </code></pre>
  
  <p>Can anybody point me to the probable problem point?</p>