I dont have any issues with the login. -> Using FireFox 3.6.12
But in another Browsergame I had a similar problem. It was a serious Lag with gameplay.google or something. The problem was fixed, when I deactivated the Plugin Greasemonkey. I'm not shure whether it was the plugin or not, but since it is deactivated on that page, the problem never occured again.
Maybe you have a plugin active that messes something up?