app.configure(function(){
  app.set('db-uri','mongodb://xxxx:xxxx@dbh00.mongolab.com:27007/testing');
  // ...
});

db = mongoose.connect(app.set('db-uri'));
var mongo_connection_details = { dbname: db.db.databaseName,
           host: db.db.serverConfig.host,
           port: db.db.serverConfig.port,
           username: db.uri.username,
           password: db.uri.password,
           collection: "sessions"};

// mongo session store
app.use(express.session({store: mongoStore(mongo_connection_details)}));


// using all the latest version of connect-mongodb, express and mongodb driver and mongoose.

// works very well locally, but using mongolab or mongohq it hangs when it tries to write the session