sessions not saved when socket.io starts

I have strange problem and I don't have any clue whats happening. Somehow sessions are not saved to redis anymore when I start socket.io, but when I comment out socket.io they work. The code can be found here: nothing unusual. This code stopped working after a db crash. When I tried to run the app again, it said that redis connection is already in use. I found and killed the node process that was using this connection, and I'm able to start my app again, but now there is this issue with sessions.

var config         = require('./config')
  , express        = require('express')
  , routes         = require('./routes')
  , RedisStore     = require('connect-redis')(express)
  , sessionStore   = new RedisStore(config.redis)
  , app            = express.createServer();

app.configure(function () {
  app.use(express.static(__dirname + '/public'));
  app.use(express.cookieParser('keyboard cat'));
  app.use(express.session({
    secret: config.sessionSecret,
    key: 'express.sid',
    store: sessionStore
  }));
  app.use(express.bodyParser());
  app.use(express.methodOverride());
  app.use(app.router);
})

app.configure('development', function () {
  app.use(express.errorHandler());
});

app.enable('jsonp callback');

routes.init(app);

app.listen(config.port);
console.log("listening on port " + config.port);

// socket.io
var io = require('socket.io').listen(app);
io.configure(function() {
        io.set("polling duration", 10);
        io.enable('browser client minification');
        io.enable('browser client etag');
        io.enable('browser client gzip');
        io.set('log level', 3);
        io.set('transports', ['xhr-polling']);
    }
);